A. O. Vet. Fak. Derg. 35 (2-3): 497-511, 1988
PATHOGENESIS, HlSTOLOGY, AND HORMONAL DEPENDENCY OF RAT MAMMARY NEOPLASMS INDVCED BY ORAL ADMINISTRATION OF
HYDRAZINE-NITROFURAN ANALOGS
Erdoğan Ertürk! Don B.Headley2 George T.Bryan3
Hydrazine-Nitrofuran türevierinin ağız yolu ile \'erilmesi sonu sıçanlarda meydana getirilen meme tiimörlerinin patojenik geli~iıni, histolojisi \e hormonal bağımlılığı
Özet: Sinıetrik veya asimetrik hidrazin türevIerinin çeşitli
rodent-lerde kolon, akciğerler ve karaciğer dahil, birçok organda kanserojen
olduklarınm ortaya konmasmdan sonra; buna karsinojen nitrofuran veya
amino analoglannm eklenmesiyle ne gibi bir değişme olacağı
araştmI-mıştır. Değişik bir tümör türü olarak, sıçanda meme kanserlerinin
meydana getirilmesi; bu tümör/erin oluşumunda başka faktörlerin etkili olabileceğini düşündürmüş ve hormonlarla ilişkileri üzerinde durulmuş-tur. Bu amaçla koruyucu, ya da sağıtıcı etkisi umulan yumurtairkIarın
çıkarılması operasyonuna başvurulmuştur. Ayrıca, yumurtairkIan alman
bir kısım sıçana östrojenin dıştan verilmesi SOI1U, ortadan kaldınlaız bu
etkinin sonradan sağlanıp sağlanamıyacağı da araştınlmıştır.
Karsinojen olarak kullal1llan, 2-hidrazino-4-( 4-aminofenil)
-tiya-zol (APT) maddesi, sıçanlarm yemlerine ağırlık itibariyle
%
0.01oranında katılarak verildikte deney hayvanlarınm
%
68 inde (34/ 50)meme tümörü meydana getirmiştir. Onuncu haftadan itibaren büyümeye
başlayan tümör/erin
%
48'i (14/29) süt bezi veya kanalrnı döşeyenepi-telden köken almış adenokarsinonı, arta kalan 15 tanesi (% 52) ise fib-roadenom yapısı göstermiştir. Diğer bir grupta, 50 sıçan m 29 tanesinde oluşturulan meme tümörleri gelişmeye bırakılmıştır. Bunlar arasıııda 18
olayda, çaplarının 2 cm yi geçmesinden sonra ooforektomi operasyonu
yapılmıştır.
1 Prof. Dr. U.O. Veteriner Fakültesi Patoloji Anabilim Dalı, Bursa-Turkey 2 Araş. Gör. Department of Human Oncology, Clinical Science Center, University of Wisconsin, Medical School, 600 Highland Ave. Madison, Wl. 53792 U.S.A.
3 Prof. Dr. Department of Human Oncology. Clinical Science Center, University of Wisconsin, Medical School, 600 Highland Ave. Madison WL 53792 U.S.A.
498 E. ERTÜRK - D. B. HEADLEY - G.T. BRYAN
Bu sıçanlarda hormonal kontrolün ortadan kaldmlmasll1a rağmen
sağlfıcı bir etki sağlanamadığı bu sıçanlarda tümör küçülmesi veya dö-külüp regresyona uğraması gibi bir değişim görülmemekle anlaşTlnuştır. Bir başka grupta ise (Gr.3), 44 sıçanm 24 ünde oluşan meme tümörleri
7 ~ıçanda gelişip çaplan 2 cm'yi geçmiştir. Bunlarda uygulanan
endok-rin ablasyonu, poliöstradiolfosfat (PEP-estron)ul1 2 mg / kg oranmda
verilmesiyle giderilmeye ve hormonal etkinin geri getirilmesine çabşıl-mış ancak tümörlerde bir regresyon şekillenmel1liştir. Bu sonuçlar
oofo-rektominin sağıtıCl bir etki yapamadığmı açıkca göstermiştir. Diğer
taraftan, profilaktik amaçla yapılan ooforektominin tümörlerin meydana getiriliş süresinde, büyüme ve malignitelerinde, bir sıçanda gelişen tü-mör sayılarında azalmalar meydana gelmiştir. Diğer bir grup sıçaıılarda
PEP enjeksiyonları (östrojen) neticesi kanserojenin etkisinin tekrar
yerine geldiği ve tümör/erin sayı ve malignitelerinde artışlar olduğu or-taya çıkn1lştır. Bu sonuç, koruyucu ooforektomi ile risk altmdaki kim-selerde, meme kanserilıin önlenebileceğini işaret etmektedir.
Summary: Hydrazines, eitlıer symmetrically or asymmetrically
substituted wifh active moieties are well known rodent carcinogens,
inducing neoplasms in colon, lungs and liver. Nitrofurans are alsa known chemical carcinogens, inducing variety of tumors in rodents, and many other experimental anima/s. In this study, the analog of nitrofuran
car-cinogens, aminophenyl-thiazole derivative of hydrazine (APT) was
tested for its carcinogenicity, and the effects of estrogens on the
induc-tion of mammary tumors in rats.
The results showed that APT is a strong chemical rat mammary carcinogen, inducing high incidence of adenocarcinomas, that are stron-giy estrogen dependent, since the oophorectomy peıformed prior to
car-cinagen administratian prevented the induction of mammary
adenocar-cinoma; and had no effect
if,
applied af ter the induced adenocarcinomas grew up to a size of 2. O cm in diameter. However, if polyestrodiaphos-phate (P EP) is given s.c. to prophylactically ab/ated rats, the full stren-gth of APT carcinogenicity H/as retumed.Introduction
Hydrazine as İn saIted form (3, 13, 30), as a1kylated symmetri-eally (5, 17, 18, 24, 28, 29), or asymmetrİsymmetri-eally (25,29, 32), and İn the hydrazide form of same organie aeids like ma1eİe (29), or formie acid (4, 6-10, 16; 32), or even in same other more complexstruetures (15,
sıÇANLARDA MEYDANA GETİRILEN MEME TÜMÖRLERI 499
31) has been reported to be eareinogenie when administered in the food or drinking water, or even by s.e., injeetions to the rats and miee of several strains of both sexes at anyage. Hydrazines were first des-cribed organotropic eareinogens indueing adenoma and adenoear-cinoma arising in the epithelial lining of large bowel of rats (S, 22, 23). But, the later reports revealed that hydrazine derivatives were equally eareinogenie for lungs (3, 2S, 32), liver (30), and many other organs (28, 31, 32) if suitable dose is provided. On the other hand, hydrazines are found in some natural food plants like edible mushrooms (31, 32), and in the environment as the results of their long time use as herbicides (29) or jet probpellant and rock et fuels (12, 28).
During the eourse of our previous studies involving S-nitrofuran eompounds, some analogs, that mayaıso be considered as the deriva-tives of hydrazine, were also found to exhibit eareinogenieity (4,6-10,
14-16). These were asymmetrieally substituted and eontained S- nit-rofuran nucleus in one side and acid or an alkyl radieals on the oppo-site end of the hydrazine. The eareinogenie potential was not equal for all these eompounds as some asymmetrieally substituted analogs were devoid of this eharaeter (16). Formylation (lS, 16). methylation (9), or unsubstituted hydrazine (9, 16) eonveyed the resulting eareino-gens towards different organs or tissues that included gastro-intesti-nal traet, liver, pancreas, lungs, kidneys and adregastro-intesti-nals, ovaries and ute-rus, and most interestingly the mammary glands and milk duets' epithelial lining that were not previously reported as being serious1y attaeked by other hydrazine eareinogens (4,7-9, ıS).
Indueed mammary tumors included fibromas, fibroadenomas and all struetural variation of glandular or duetal adenomas and adeno-eareinomas that were s.e., transplantable and probably somewhat hormone dependent (15), similar to those observed in some other
01'-gans (34), and sinee the deaeylation can oeeur (33). Among those tes-ted hydrazine-nitofuran eompounds, the alkylated analog (9) exhi-bited the highest earcinogenie aetivity for the breast tissues, and this may be due to the additional power furnished by alkylation that eom-pares with little (IS) or no aetivity of similar analogs (16) that had the hydrazine bu ried deep into the ehemieal strueture.
The existenee of fibroadenomas with varied amounts of epitheli-al and stromepitheli-al elements, the inereasing rate of histologie malignaney refleeted by inereasingly prominent anaplastic nature of seeondary or
500 E. ERTÜRK - D. B. HEADLEY - G.T. BRYAN
further generations of transplanted tumors grown in the recipient rats, and the observatio~ of some dependence of viability of these trans-planted tumors on the sex of the recipient (15) all suggested the possib-le hormonal dependency of these mammary neoplasms (15, 34). like those induced by different chemical carcinogens (26).
APT induced a very high mammary tumor incidence with the shor-test required Iateney period (9), and it was selected as the hydrazine containing carcinogenic chemical to study the pathogenesis, clinical and histological behaviour, and the hormonal dependency of mammary neoplasms that would be reflected by their maintenance and growth rate variations stimulated by endogenous or supplemented estrogens, and this paper reports these observations.
Materİals and Methods
A total of 340 female weanling Sprague-Dawley rats (Sprague-Dawley, Madison, WL) were randamly allocated into LO groups, and were fed ad libitum either unmedicated control diet of Wayne Lab Blox (Allied Mills Ine., Chicago III.) or the same diet with 0.01 /~ (w / w) APT for 66 weeks, [ollowed by unmedicated control diet until the experiments ended (Table I). Other treatments included ovariec-to my prior ovariec-to the experiments start (groups 5 through 10) or after the development and growth of mammary tumors larger than 2.0 cm in diameter (groups 3 and 4); and estrogen replacement therapy for eit-her the whole experimental period (groups 7 and 8) or shorter durati-ons (groups 9 and 10). Ovariectomies were performed under the et her anesthesia, by making bilateral incisions in both flanks to ligate, and excise the ovaries. Completness of ovariectomies was confirmed by vaginal smears taken for 5 days post surgery and those rats showing estrous on the last three days were removed from the study. These vaginal smears were continued at monthly intervals throughout the entire treatment period. Completness was also confirmed at the time of necropsy. Estrogen replacement therapy consisted of injections of every 14 days of polyestradio! phosphate «PEP) Estradurin, Ayerst) at a dose of 2 mg / 100 g body weight in 0.2 ml of sodium phosphate-nicotinamide buffer. All rats received prophylactic Lm., injections of 0.1 ml of Benzathine penicillin G (Wyeth) every LO weeks. Experi-mental anima!s were palpated weekly for developing tumors starting on the LO th week of APT feeding since the first rat mammary tumor a previous study appeared at this time (9). The tumor growth was
mo-sıÇANLARDA MEYDANA GETİRILEN MEME TÜMÖRLERI 501
----/--'" ..•.. ",---'"
"-
--_._. __ 1"".--. -.,-'
300 350 r 1 2 APT 3 APT-RO 4 APT-Po S An-pc-PEso
.~o
it 8ız "
zo ~ 28 32 ~ 'tO ew 'it 52. şi,'D
•
~~S (Cessation of medieated diet)
Chart. Growth curves for treatment and control rats. Detailed descriptions of treatments for the rat groups are found in table ı.Rats were weighed every 4 weeks and the mean we-ights of all surviving rats are recorded. Mean weights of rats in groups 4 and 5 remained very similar to those of rats in groups 3 and 6, respectively. The mean weights of groups 8, 9, and LOmts were within 10 %of the mean weights of group 7 rats. All rats receiving APT were placed on unmedicated diets after 46 weeks. Estrogen treatments were caesed
at weeks 20 and i8 for groups 9 and iO, respectively.
nitored by taking weekly measurements with calipers along the two perpendicular exes, one of which was always the longest dimention of the neoplasm. Animals were weighed and food consumptions were estimated every four weeks. Rats dying during or killed at the end were necropsied and the representative tissue or tumor samples were prepared for light microsropy as described earlier (9).
502 E. ERTÜRK - D. B. HEADLEY - G.T. BRYAN
Results
Although the survival times were similar, the growth rates varied (Chart) among the group s depending upon the additional therapies that included ovarieetomy prior to or after the start of APT admi-nistration, and short or long time hormon supplementation (Table 1). Despite its high toxicity observed in a previous study (9), APT at this dosage did not eause any severe growth retardation. Remedial endoe-rine ablation seemed to have no effeet on either the food eomsumption or the growth rate of rats, if aehieved by bilateral removal of ovaries
Table ıTreatment Groups Rats with tu-ı
mor /survivors Number
Group Evaluated his- of rats at Remedial
No: tologically start ovarieetomy Treatment
--
--i 9/29 30 Fed control dieta
2 34/50 50 Fcd APTb
~ 29/50 50 18/29 Fed APT +remedial oopho-rectomyC
4 24/44 ~O 7/24 Fed APT+- remedialoopho-reetomy + estroned
5 3/28 30 Fed control diet +
prophylac-tic oophoreetomyC
6 3/50 50 Fed APT + prophylactic
oop-21 ;'33 horectomy
7 35 Fed APT-I-prophylactic
oop-horeetomy +estrone
8 5/15 15 Fed APT -i- prophylactic
oop-horeetomy+ estrone (20 wks) f
9 7/13 15 Fed control diet -+-
prophy-lactie ooplıoreetomy -+- est-ro ne
10
i
6/14 15 Fed Control diet +
prophy-lactic oophoreetomy -+- est-rone (l8 wk)
a) Control diet consisted of Wayne Lab Blox and water ad Jibitum.
b) 2-Hydrazino -4- (4- aminophenyl) thia:wle (APT) was fed ad Jibitum at a dose of 0.10
%(w / w) in ground Wayne Lab Blox for.46 weeks. Thereafter the rats were fed ummedi-cated control diet.
c) Remedial bilateral oophoreetomy (RO) was performed when the rat had amammary tumor diameter of 2 cm.
d) Estrone in the form of Polyestradiol phosphate was given as biweekly S.c. injections at a dose of 20 mg / kg beginning on the day of oophoreetomy and extending throughout the length of the experiment unless indicated otherwise (see groups 9 and LO).
e) Prophylactic bilateral oophoreetomy (PO) was performed 6 days prior to feeding of APT diet or, for control rats, unmedicated diet.
sıçANLARDA MEYDANA GETİRİLEN MEME TÜMÖRLERİ' 503
after the induced tumors grew up 2.0 cm in diameter size. However, prophylactic bilateral ovariectomy (prophylactic endocrin ablation), performed 6 days prior APT medication did have a remarkable posi-tive effect on the growth of female Sprague-Dawley rats since they grew as big as a male animaL. On the other hand, the observation of the slo-west growth rate for rats similarly treated but received additional PEP therapy to replace the delated endogenous estradiols, was also somew-hat unexpected. This effect may be the result of excessive and continu-ous supplementation of sex hormones to compensate the preablated endogenoLls estragens. The duration of PEP administration was im-portant and this was evidenced by va ried tumor incidences in groups 8 and iO (Table 2).
Negative control rats (Group 1) (Tables i,2) spontaneously de-veloped one mammary adenocarcinoma, six mammary fibroadenomas and two subcutan fibrosarcomas occurring after a long latent period (53 ::t 16 weeks). This compares with the statistically highly signifi-cant mammary tumor indicence (34/ 50) resulting from the carcino-gen APT medication in group 2. The required latent period was 10 weeksthat was much shorter than controls. Of these 29 breast tumors, 14 were adenocarcİnomas of glandular or ductal origin; and 15 were fibroadenomas of mostly ductal orİgin and consisted of varied amounts of stromal connective tissue elements, also participated into the neop-lastic formation. Mammary adenocarcinomas if orijinated from glan-dular or alveol ar epithelium exclusively, contained very little or almost undetectable amount of stromal connective tissue, but, exhibited se-veral forms of anaplasia, mostly medullary adenocarcinomas demonst-rated 5-15mitotic figures per high power field. The histological appe-arances varied from fibroadenocarcinoma, cystic and papillary, me-dullary, and crİbriform architecture with different cell types that inc-luded glandular, fusiform, "squamous, mucous producing metaplastic epithelium. Ductal adenocarcinomas usuaIly contained more connec-tive tissue than alveolar carcinomas in even the neighboring areas of the same nodule. The histological malignancy were in agreement with the multiplicity of nodules, and the higher the number of induced no-dules the higher the grade of histologic malignancy was observed. One rat had up to 16 nodules of which some were most malignant as so-me others were benign fibroadenomas. Mammary neoplasms arising from' the ductal epithelium deve lope d into one cell lined simple fib-roadenoma with excessive connective tissue, also called simple
intra-Table 2
o Number of Rats Mammary tumor
Z Evaluated Survival Latent
pe-Histologic Classifica tion of Tumors cı.
::ı At Histologi- With in weeks riod in o Start cally Tumor P-values (X:f::S.O.) week s
..
"
(X:f::S.O.)-
--i 30 29 9 67 :f:: 9 53 ~: 16ı.
Mammary Adenocarcinoma 6. Mammary Fibroadenomas--
2 . Mammary Fibrosarcomas--2 50 50 34 P<O.OI 62 :f:: 12 52 :J: 16 14. Mammary Adenocarcinomas 15. Mammary Fibroadenomas
1. Wilms Tumor 1. Skin Fihrosarcoma 1. lntestinal Adenocarcinoma 1. Forestomach Squamous Cell Care
noma 1. Pituitary Adenoma
ı.
Uterine Leiomyosarcoma 1. Ovarian Dysgerminoma 1. Pancreatic Haemangiopericytomaı.
Thymic Sareoma1. Thymic Ductal Adenocareinoma
-- --
--- ____ o3 18 18 LS 64 :f:: 6 46 :f:: LO 8. Mammary Adenocarcinomas 7. Mammary Adeno fibromas 3. Mammary Fibromas
--4 7 7 7 62 :f:: 6 46 :f:: 8 3. Maınmary Adenocarcinomas 3. Mammary Adenofibromas
ı.
Mammary Fibroma --S 30 28 3 P<0.05 70 :f:: 4 65 :f:: 11 2. Mammary Fibroadenoması.
Mammary Fi brosarcomaı.
Periana! Gland Adenoma-- --
--6 50 50 3 70 ..L~ 5 71 _i.~ O 1. Mammary Fibroadenoma
ı.
Kidney Nephrob\astoma 1. Uterine Leiomyosarcoma ----
----7 35 33 21 49 :f:: LI 35 ~ı:12 6. Mammary Adenocarcinomas 2. Mammary Fibröadenomas 3. Pituitary Adenomas 1. Uterine Adenocareinoma 3. Uterine Leiomyosarcomas3. Uterine Squamous Cell Cameinom, 2. Vagina\ Squamoııs Cell carcinomas 1. Lacrima\ Gland Adenoma
ı.
Thymus Ouctal Adenocareinoma--
--
____ o 8ı5
15 5 47 ::l: 9 38 ::f: 12 2. Mammary Adenocarcinomas 1. Mammary Fibroadenomaı.
Mammary Fibroma 1. Pituitary Adenomaı.
Uterus Leiomyosarcoma--
-9 15 13 7 56 :J: 7 45 -I- LO 2. . Mammary Adenocarcinomas
ı.
Mammary Fibroadenoma 1. Pituitary Adenocarcinoma i. Pituitary Basa\ Adenocarcinoma 2. Pituitary Chromophobic Adenocareinomas
ı. Vagina\ Squamous Cell Carcinoma
ı.
Thymus Squamous CeII Carcinomaı.
Thymus Ouctal Adenoma-- -- ----_.
10 ]5 14 6 58 ::f: 8 54 ..L O
ı.
Mammary Fibroadenoma-4. Pituitary Chromophobic Adenomas 5. Pituitary Basal Adenocarcinoma
sıÇANLARDA MEYDANA GETİRİLEN MEME TÜMÖRLLERİ S05
eanalieular fibroadenoma, or with papilIary projeetions into the milk duet that is similar to duetal papilloma with an abundant stroma sur-rounding these proliferations, or without alimiting basement membra-ne or eonmembra-neetive stromal wall around to prevent the invasion of sur-rounding stroma whieh is seen in duetal fibroadenoeareinomas or adenoeareinomas. in a few ca~es, both the epithelial parenehymal eells and the fibroblastie stromal eells exhibited severe anaplasia and marked mitotie aetivity index to be classified as eareinosareomas. ln-terestingly, the duetal tumors with lesser epithelial elements were more likely benign fibroadenomas eve n close to a fibroma, eontrary to glan-dular tUl110rs that did always cxhibit a malignant histology, as no bc-nign adenoma was deteeted in this series.
The remaining 10 indueed neoplasms were of different origin ari-Siııg from gastrointestinal, genito-urinary, and endoerin or exoerin glandular epithelium with a highly statistieal importanee (p>0.0i) (Table 3). The induetion of genito-urinary and endoerin or exoerin neoplasms by APT indieates the relationships between its eareinoge-nieity and the produetion of a hormonal imbalanee in the medieated female rats body.
In group 3, twenty-nine of 50 rats (58
%)
developed mammary neoplasms, and 18 of these grew up 2.0 cm in diameter size for reme-dial endoerin ablation; and none of these eighteen ovarieetomized rats demonstrated any change of size or eolor and consisteney indicating the regression due to the removal of sex hormones (Tables 1.2).In the next group that had 24 mammary tumor eases in 44 evaluated
rats, only seven animals were ovarieetomized after the tumors reaehed the required size. These seven rats reeeived PEP injeetions to recover
Table 3. X2 Values for Mammary Tumor Incidence by Group (a)
Group 1 2 3 4 5 6 7 8 9 10 ---
--
-- ---- --
-----
----
--ı 10.1 3.5 8.9 2 23.6 41.2 0.17 0.91 3 0.56 4 5 6 7 1.4 6.25 8 0.33 9 0.28 i 10sur. E. ERTÜRK -' D. B. HEADLEY - G.T. BRYAN
from ereated hormonal imbalanee, also exhibited no turnor regression, as the result of hormon supplementation. These results indieate that, the remedial endoerin ablation has no useful effeet to regress the al-ready developed or ehernieaIly indueed mammary neoplasıns in the rat.
Prophylaetie ovarieetomy, on the other hand, had profund ef-feets in the induetion, the growth eharaeteristies, multiplieity, and on the grade of malignaney of either spontaneously developing (in group 5) or APT-indueed (in group 6) mammary tumorso In group 5, three of 28 evaluated rats developed tumors, of whieh 2 were Iate oeeurring mammary fibroadenomas that are known to be eontroIled by pitui-tary growth hormone (2), and one was subeutan fibrosareoma (Table 2). In the test of prophylaetie endoerin ablative approaeh in the tre-atment of mammary eaneer, the group 6 gaye us very important re-sults eonfirming the etTeets of estradiols on the induetion of mammary neoplasms. Contrary, the results obtained from groups 2 (mueh hig-her tumor incidence without ovarieetomy), and 3 (no remedial aetion from ovarieetomy performed after the induetion of tumors), the sta-tisticaIly insignifieant tumor incidence (even smaIler than the control s value) was observed. This effeetive result was further strengthened by the increased tumor incidence in the seventh group after reestablisment of hormonal imbalanee by PEP injeetions (Tables I, 2). Group seven rats had a statistieaIly highly signifieant (21 out of 33) incidence of early oeeurring and mostly anaplastie adenoeareinomas of mammary or other genital organs and in some other glands. The duration of the estrogen supplementation was also important here, and this is seen in the resulting lower tumor incidence due to the shorter time of PEP in-jeetions in the group 8 (5 out of LS rats had tumors). This hormon al dependeney was further evideneed by the last two control groups (9, and
ıo)
that were used to evaluate the eompensation of the ablated estradiol aetivity, by exogenous supplementation of this hormone for the duration of APT -medieation, or in a rcasonably shorter ter m (66 wks vs 20 wks.). As the result, both groups had tumor ineidenees hig-her than the untreated eontrols. This favored the longer period of PEP administration (dose-time etTeet), sinee more and malignant tumors were observed in group 9 (Tables l, 2), and by the induction of endoerin gland tumors, espeeiaIly pituitary neoplasms that are known to be closely related with ovarian hormones (2).sıçANLARDA MEYDANA GETIRiLEN MEME TÜMÖRLERİ 507
Discussion
The molecular basis of the carcinogenicity of hydrazine nitro-furan derivatives is not known at this time. This group of compounds contain a hydrazine nucleus which is a well established careinogen (3, 5, 17, 20, 21, 24, 25, 27, 32), and either a 5-nitrofuryl or 5-nitrop-henyl-thiazole, or else an amino form of these derivatives that cons-titute another carcinogenic portion (6, 10, 14, i6) in their chemical structure. The metabolism and biotransformation of 5-nitrofuryl-thiazoles involve the n-hydroxylation of 5-nitro moiety which may be carried out by several enzyme system s including nitroreductase, mixedfunction oxygenases (cytochromes, xanthine oxidase) and pros-taglandin endoperoxide synthetase (4, 6, 33). On the other hand, hy-drazines have been reported to follow totally different pathways (1, 6, 12, 13, 18, 20-22, 24, 28) including nuclephylic-electrophylic subs-titutions by producing free radicals from their alkylated forms. Ho-wever, i, l-dimethylhydrazine was found less carcinogenic than hyd-razine sulfate or chloride (25) those have capability to ionize and pro-duce a positively charged hydrazine that can attack to any biologi-cally important macromolecule with nucleophylic character (1, 12,
13, 18). Monomethylhydrazine was noncarcinogenic (25) compared with i,l-dimethylhydrazine when they were tested in mice. This dif-ference may be understood if they were considered as alkylating age nt s (i, 20). This concept fits equally well to the observation of the highest tumor incidence induced with the asymmetricaIly substituted nitro-furyl-thiazole hydrazines represented in our series by DMNT, a st-ructure that has two methyl radicals on the hydrazine nucleus (16). There is a marked number evidence supporting the idea that substitu-ted hydrazines are metabolized to act.ive metabolites via deacylating enzymes present in most tissues (33) which is a corollary to the fact that hydrazines produce tumors in a large number of organs or tissu-es (25, 27, 32). We reported the high incidence of mammary tumor pro-duction by hydrazine derivatives (6-9, 14-16) for the first time, ex-cept Severi and Biancifiori (27) who showed another hydrazide to in-duce mostly lung together with some breast tumorso Despite the fact, that hydrazines were kept responsible from the beginning, as to car-cinogen for colon epithelium, this kind of neoplasms were not obser-ved in our series (14-16). This difference may an indication of diffe-rent available metabolic pathways for differently substituted hydrazi-nes acted as carcinogens.
508 E. ERTüRK - D. B. HEADLEY - G.T. BRYAN
The pathogenesis, and histological characteristics of mammary neoplasms induced by APT in this study were not different than those induced by other carcinogens including 5-nitrofurans (6-9, 14-16), salted (3, 13, 30) or alkylated hydrazines (5, 17, 18, 20-29, 32), or other chemicals (26). )The hormonal dependency of rat mammary tumors induced by APT was refleeted by the lower incidences fol-lowing the prophylactic ovarieetomy performed in groups of rats with or without the supplementation of ablated endogenous estradiols. In a prophylaetieally ovarieetomized group, APT administration did not result in a statistically significap.t tumor produetion, in faet, the number of tumors and the tumor bearing animals were lesser than those of controls; However, the PEP administration effeetively cor-reeted this tum or inhibiıion, provided sufficiently long time and su-itable dose response. In so me other control rat s used to evaluate the effeets of hormon alone, estradiol induced statistically significant tumor incidence, even without the administration of APT as the ear-cinogen. The remedial endocrine approaeh however, was not seem to be fruitful sinee no tumor regression was observed in rats ovariecto-mized after the indueed tumors reaehed 2 cm. in diameter size.
The growth rate of rats were signifieantly altered by the ereation of hormonal imbalance by prophylaetie ovarieetomy, and this was seen in female rats growing as big as a male animal even despite the administration of toxie (16) and earcinogenic APT. The rat s similarly treated but reeeived additional estradiol supplementation appeared as the slowest growing, and reaehed the size of negative controls or groups without hormonal alteration. These results may help to un-derstand why male rats naturally grew bigger than opposite sex, or females growing the ablation of ovaries. Hormonal imbalanee may sometimes be the result of long term use of hormon-containing drugf>, like eontraceptives in everyday use, and may create some important
N
H
i
:N H
sıçANLARDA MEYDANA GETİRiLEN MEME TÜMÖRLERİ 509
problems if it occurs simultaneously with some e,ıvironmental fac-tors thatcan act synergisticalIy to enhance and make it strong enough to induce tumors of mammary, pituitary or any other gland or tissue origin.
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