Comparison of effects of different combined oral-contraceptive formulations on carbohydrate and lipid metabolism

Oral glucose-tolerance tests were performed and fasting serum cholesterol and triglyceride levels measured in 1628 Caucasian women taking combined oestrogen/progestagen oral contraceptives (o.c.) and 577 women not taking O.C. The former were divided into six groups according to the composition of the O.C Glucose tolerance deteriorated in all O.C. groups containing oestrane progestagens (nortestosterone-derived) or the gonane, norgestrel, but was unaltered by O.C. containing a pregnane progestagen (derived from progesterone). The greatest deterioration was with O.C. containing 75 microgram or more oestrogen, and this was associated with impairment of the early insulin response to glucose. In O.C. containing a pregnane progestagen insulin secretion was unaffected. In the remaining O.C. groups insulin secretion was increased; this was most pronounced with the O.C. containing a gonane progestagen. Serum-cholesterol was elevated only with O.C. containing 75 microgram or more oestrogen and an oestrane progestagen and tended to be lower in O.C. containing a gonane progestagen. O.C.-induced hypertriglyceridaemia was oestrogen-dose-related, and this effect was potentiated by the pregnane progestagen. The gonane progestagen antagonised oestrogen-induced hypertriglyceridaemia.

Contraceptive steroids and coronary artery atherosclerosis in cynomolgus macaques

The influence of two types of steroidal contraception on the extent of coronary, aortic, carotid, and iliaco-femoral atherosclerosis was assessed in 57 cynomolgus macaques with moderate diet-induced hyperlipoproteinemia. Thirteen animals were treated with an intravaginal ring that released 17 beta-estradiol and levonorgestrel. Fifteen females were treated with an oral contraceptive (OC) composed of ethinyl estradiol and norgestrel. Fifteen females received placebo vaginal rings, and 14 males were untreated. The contraceptive treatments resulted in similar large reductions in plasma high-density lipoprotein (HDL) cholesterol concentrations. Neither treatment influenced the prevalence of coronary artery atherosclerosis. However, treatment with the contraceptive vaginal ring was associated with increased extent of coronary artery atherosclerosis (plaque size) relative to untreated females, whereas treatment with the OC was not. The contrasting effects of the two treatments could not be explained by differences in total plasma cholesterol, HDL cholesterol, or blood pressure. The results suggest that the greater estrogenic influence associated with the ethinyl estradiol-containing OC resulted in inhibition of coronary artery atherosclerosis despite a pronounced progestin-induced lowering of plasma HDL cholesterol concentration and, further, that hormonal balance may have a marked influence on the relationship between plasma lipids and atherogenesis.

Comparative aspects of contraceptive steroids--effects observed in beagle dogs

The effects of oral contraceptives have been studied in the beagle bitch for periods up to 7 yr. High doses of these potent estrogen: progestogen (E:P) combinations have been shown to promote tumors in the mammary glands, smooth muscle of the tubular genitalia, and occasionally in the transitional epithelium of the neck/trigone area of the urinary bladder. The contraceptive formulations used in humans are balanced with an E:P ratio of about 1:5 to 1:80 to produce a desired decidual response in the uterus. The corresponding ratio for producing the decidual reaction in the dog is 1:1,000 to 1:3,000 with the result that the dog is grossly overdosed with estrogens when given the human formulation at the usual multiples of up to 25 times the human dose. Smooth muscle tumors of the tubular reproductive tract are common sequelae to estrogen overstimulation in the dog and are known to occur in other species, including the humans. The dog also has major differences in hormonal control and sensitivity when compared to humans. Progestogens stimulate synthesis and release of growth hormone (GH) in dogs which in turn is the major stimulant (with progestogens) of mammary growth and tumors. Evidence is accumulating which indicates that most if not all progestogens can produce mammary tumors in the dog if given by the correct route and at high enough dosage. In contrast, GH in humans is not increased nor does it have any significant mammotrophic role. Mammary tumors in dogs related to oral contraceptives are now widely considered to be irrelevant as a model or predictor for human tumors. Transitional cell tumors in the urinary bladder seem to be a species specific phenomenon seen on occasion in the dog, but not in the rat, monkey, or human. The usual location in the neck/trigone area may be related to the embryologic origin of this portion of the bladder, which derives from tissues more closely related to the genital organs than does the rest of the bladder.

Comparative aspects of contraceptive steroids: effects observed in the monkey

The use of the non-human primate in long-term studies of contraceptive steroids has been questioned because of time, expense and apparent lack of results predictive for humans. Controversies have arisen primarily over the occurrence of mammary nodules in studies of different contraceptive steroids and the occurrence of uterine tumors in 2 high-dose group monkeys in the Depo-Provera study. The long-term studies have been criticized because of the experimental design and the small number of monkeys per dose group. Individual studies by themselves did not reveal lesions other than those expected from an exaggerated pharmacologic response of target tissues; however, a pattern may emerge from reviewing and combining results of different studies that indicate the results of these studies are in agreement with the clinical findings in man. Effects of contraceptive steroids on the mammary gland and genital organs will be discussed. Data from 17 contraceptive steroid studies involving 264 untreated control and 733 treated non-human primates were available.

Effects of prolonged administration of the 19-nor-testosterone derivatives norethindrone and norgestrel to female NZB/W mice: comparison with medroxyprogesterone and ethinyl estradiol

To evaluate effects of commonly used progestational estrogenic contraceptive steroids in a hormone-responsive model of lupus, we treated female NZB/W mice before clinical disease (6 wks of age) and after onset of lupus (24 wks of age) with doses of hormones titered to suppress reproduction. We report efficacy of norethindrone (NE) and norgestrel (NG), progestins derived from 19-nor-testosterone, in delaying expression of anti-DNA antibodies. Mice implanted with NG at 24 wks of age had prolonged lifespans. In contrast, the hydroxyprogesterone derivative, medroxyprogesterone acetate (MP), did not affect autoimmune disease. These observations suggest that prolonged administration of 19-nor-testosterone derivatives, in small doses adequate to suppress reproduction, may have ameliorative effects in systemic lupus erythematosus. Mice receiving ethinyl estradiol (EE) plus courses of tetracycline to suppress cystitis had active anti-DNA responses. In 60% of EE-treated mice, however, early deaths resulted from malignant lymphomas and complications of obstructive uropathy. Estrogen toxicity, rather than accelerated lupus, was the major cause of death in NZB/W mice treated with EE.

Problems in evaluating chronic toxicity of contraceptive steroids in dogs

The long-term effects of oral contraceptive steroids including a combination of norethindrone and ethynylestradiol, a sequential regimen of dimethisterone and ethynylestradiol, and daily administration of megestrol acetate were studied in female beagle dogs at dose levels of 1, 10, or 25 times the projected human dose levels. The major findings included cystic endometrial hyperplasia and pyometra requiring hysterectomies and alopecia for the norethindrone-ethynylestradiol and dimethisterone-ethynylestradiol treated dogs. These groups did not have accentuated mammary development or treatment-related hyperplastic or neoplastic changes. For dogs given dimethisterone-ethynylestradiol, numerous acne-like lesions occurred in the skin of the mammary areas. Dogs given the higher dose levels of megestrol acetate had marked mammary stimulation, hyperplastic and neoplastic changes in the mammary glands, and clinical and pathologic changes typical of diabetes mellitus. Mammary changes of nodular hyperplasia, benign mixed tumor, and adenocarcinoma appeared as distinct entities although constant and intense mammary stimulation may be a common denominator. Such mammary changes have not been found in long-term studies in monkeys or rats with megestrol acetate, and the relevance of the canine mammary changes to projecting potential tumorigenesis in women is questioned.

Regression of pathologic changes induced by the long-term administration of contraceptive steroids to rodents

The induction of pathologic changes with hormone steroids has been studied in rodents, although comprehensive studies are lacking on the potential reversibility of these lesions. For these purposes, groups of rats were treated with quingestanol acetate and quinestrol, a progestogen-estrogen combination, for 50 weeks and observed for a subsequent 30-week period. Treatment resulted in a significant body weight gain suppression and reduction of food consumption which recovered after withdrawal. Other significant treatment-related effects were hair loss, ataxia due to pituitary enlargement, mammary chain masses with histologic adenocarcinoma, lens opacities, ovarian atrophy with follicular arrest, and uterine atrophic changes with suppurative inflammation throughout 50 weeks. Cessation of treatment did not effect hair loss or lens opacities, while mammary chain masses decreased in size and in incidence; mammary gland tumors showed regressive changes including the disappearance of adenocarcinoma, and the incidence of ataxia diminished together with reduced pituitary weights. Chromophobe cell hyperplasia with decreased eosinophils and acidophils and hemorrhage into the pituitary was observed up to 50 weeks and the tinctorial affinity of basophils and acidophils returned after withdrawal. Ovaries and uteri, which become atrophic and sustained chronic suppurative inflammation in the treatment phase, showed reduction of inflammatory reaction and disappearance of suppuration after withdrawal, and endometrial regeneration occurred with luteal cells seen in the ovaries. These results revealed the regressive characteristics of some of the mammary gland carcinomas as well as steroid-induced endocrine and pathologic lesions other than tegumentary and ocular changes in rats receiving high levels of steroids for prolonged periods of time.

Influence of endogenous and synthetic female sex hormones on human blood cells in vitro studied with comet assay

The comet assay has been conducted with numerous cell lines to assess in vitro genotoxicity. In order to use the comet assay as part of an in vitro test for evaluating genotoxicity, however, there are cell-specific factors that need to be better understood. In this present study we have evaluated some factors that may impact upon the DNA damage detected in whole blood (WB) cells and lymphocytes (ILs). Experiments were conducted comparing responses of both cells, and investigating the effects of the female hormonal cycle, and oral contraceptive (OC) use on DNA damage detection in the in vitro comet assay, at three sampling time. No significant differences were detected in the basal levels of DNA damage detected in ILs and WB cells from women OC users and non-users and from men. Basal DNA damage in ILs was unaffected by gender and stage of the menstrual cycle or the stage of the treatment schedule. Our results also indicated that the H2O2 induces DNA damage in human lymphocytes independently of gender, low-dose OC use and hormonal fluctuation. However, data showed that in 3rd sampling of menstrual cycle, lymphocytes were more resistant to H2O2-induced DNA damage than those from OC users and men.

Unscheduled DNA synthesis caused by norethindrone and related contraceptive steroids in short-term male rat hepatocyte cultures

The genotoxic potential of oral contraceptive steroids such as norethindrone was investigated in short-term rat hepatocyte cultures by measurement of unscheduled DNA synthesis. Norethindrone caused a small dose-dependent increase in unscheduled DNA synthesis in male rat hepatocytes as judged by the incorporation of [methyl-3H]thymidine into DNA. This was assessed either by liquid scintillation counting following isolation of DNA or by autoradiography. No increase in unscheduled DNA synthesis could be detected in female rat hepatocytes treated with norethindrone. Pre-treatment of male rats with phenobarbitone prior to hepatocyte preparation decreased the norethindrone mediated unscheduled DNA synthesis relative to control hepatocyte cultures while 3-methylcholanthrene pre-treatment had little effect. Unscheduled DNA synthesis in norethindrone treated control male rat hepatocytes was reduced by the mixed function oxidase inhibitors SKF 525A or metyrapone. In 24- or 52-hour-old hepatocyte cultures in which the cytochrome P-450 content was lower than in freshly prepared cells, or in a hepatocyte-derived cell line lacking cytochrome P-450, unscheduled DNA synthesis due to norethindrone was either decreased or abolished. Structure activity studies showed that only steroids containing a 17 alpha-ethynyl substituent caused an increase in unscheduled DNA synthesis.

FDA requirements for nonclinical testing of contraceptive steroids

Written guidelines for the preclinical testing of contraceptive steroids have not been revised since 1968 despite the fact that many important changes have been implemented by the FDA's Division of Metabolism and Endocrine Drug Products. This paper describes the new preclinical testing requirements and the rationale for their implementation.

Genotoxic potential of medroxyprogesterone acetate in cultured human peripheral blood lymphocytes

Medroxyprogesterone acetate was studied at three different concentrations (1, 5 and 10 microM), for its genotoxic effects in human peripheral blood lymphocyte culture using chromosomal aberrations and sister chromatid exchanges as parameters. Duplicate peripheral blood cultures were treated with three different concentrations (1, 5 and 10 microM) of medroxyprogesterone acetate. The study was carried out both in the absence as well as in the presence of metabolic activation (S9 mix) with and without NADP. Medroxyprogesterone acetate was found genotoxic at 5 and 10 microM in the presence of S9 mix with NADP. To study the possible mechanism of the genotoxicity of medroxyprogesterone acetate, superoxide dismutase and catalase at different doses were used separately and in combination with 10 microM of medroxyprogesterone at different doses in the presence of S9 mix with NADP. Superoxide dismutase treatment results in an increase of the genotoxic damage but catalase treatment reduce the genotoxic damage of medroxyprogesterone acetate. Catalase treatment in combination with superoxide dismutase also results in the further reduction of the genotoxic damage. The results of the present study reveal that medroxyprogesterone acetate is genotoxic only in the presence of metabolic activation (S9 mix) with NADP. Treatments with superoxide dismutase and catalase suggests the possible generation of reactive oxygen species by redox cycling of various forms of quinones, similar to estrogens, that are the results of aromatic hydroxylation by cytochrome P450s.

Guidelines and requirements for the evaluation of contraceptive steroids

Since their introduction in the early 1960s, the oral contraceptive (OCs) steroids have been subjected to preclinical and clinical investigations unprecedented in medical history. As a result of such extensive studies, it is now possible to make a comprehensive review of preclinical and clinical data on oral contraceptives. The OCs were introduced at a time when the Food and Drug Administration (FDA) was undergoing drastic changes as a result of the thalidomide tragedy, the introduction of the Kefauver-Harris Amendment, and the desire for greater control over the pharmaceutical industry. The initial requirements for the safety evaluation of OCs were identical to those of other drugs. There were no explicit requirements for OCs although it was generally felt that the requirements should be more stringent because the OCs were being used in otherwise healthy women for long periods of time and with minimal medical supervision. In the 1960s when it became apparent from ongoing studies that there was an increased incidence of mammary tumors in dogs treated with some progestins, the FDA made the decision to terminate clinical studies and established the requirement for 7- and 10-yr studies in dogs and monkeys, respectively. The primary purpose of this paper is to present an historical perspective of the evolution of the preclinical requirements for the evaluation of the safety of OCs prior to their use in the various phases (I, II, III) of clinical trials. Some proposed changes in the requirements are discussed. This information will form the basis for other presentations dealing with the safety assessment of OCs in rats, dogs, and monkeys.

Evaluation of the carcinogenic effects of estrogens, progestins and oral contraceptives on cervix, uterus and ovary of animals and man

Estrogens do not have the general biological effect of increasing the occurrence of cancer in various species of laboratory animals. The neoplastic effect of estrogens in animals is strain and species dependent. Estrogens may increase the incidence of uterine cervical cancer in some strains of mice, but not in other strains or other animal species. The progestins and oral contraceptives (OC) have not induced cervical cancer in animals and most studies demonstrate that the steroid anovulants do not increase the occurrence of abnormal cervical smears or cervical cancer in women. Estrogens increase the occurrence of endometrial cancer in the rabbit, occasionally in the mouse, but apparently not in other species. Case-control studies in menopausal and postmenopausal women indicate an increased risk of endometrial carcinoma (EC) associated with use of estrogen. However, in other studies estrogen has not been related to EC. Cases of EC have been reported in women using sequential OC but a causal relationship has not been established. Progestins alone may arrest progress or cause regression of EC in women. EC has not been related to use of the combination OC, and it is unlikely that use of these anovulants will lead to the development of endometrial cancer. Estrogens or OC do not induce a carcinogenic response in the ovary. A decrease in ovarian cysts, is observed during the clinical use of OC.

17-alpha-ethinylestradiol and norgestrel in combination induce micronucleus increases and aneuploidy in human lymphocyte and fibroblast cultures

Oral contraceptives are highly efficient and easily administered drugs; however, it must not be forgotten that they are composed of chemical substances which can be classified as potential carcinogens. Testing of a substance for genotoxicity represents a reliable approach both to evaluate the genetic hazard and to obtain information on its possible tumorigenic (cancerogenic) properties. The present study was undertaken to evaluate through carefully planned and controlled investigations the in vitro cytogenetic effects of oral contraceptives (ethynilestradiol and norgestrel mixed in the proportion 1:5) using three different concentrations, with two different durations of treatment (48 and 72 h), on two types of human cells (lymphocytes and fibroblasts) and a series of short-term test procedures: sister chromatid exchange (SCE), micronucleus test (MN), and chromosome aberrations (CA). In addition, the FISH procedure and in vitro anaphase and metaphase preparation analyses were performed. In contrast to CA and SCE frequencies, the frequency of MN in treated blood lymphocytes showed higher values by comparison with the controls, although the difference was statistically significant only for the lowest concentration (P = 0. 016). When using pancentromeric alphoid probes, the FISH procedure gave positive signals in more than 85% of micronuclei, clearly indicating that MN may contain whole chromosomes rather than acentric fragments. Unlike the lymphocytes, the fibroblasts showed dose-dependent effects, although those treated with the highest hormone concentrations showed an increased number of highly damaged cells (cytoplasmatic vacuolization, nuclear fragmentation, etc.), a decreased number of anaphase cells, a large number of which were abnormal, and a reduction of mitotic index. In conclusion, our data confirm that hormones do not induce structural chromosome aberrations in lymphocytes and indicate that ethynilestradiol and norgestrel have an aneugenic effect on fibroblast and lymphocyte cultures; FISH analysis on micronuclei from lymphocyte cultures and anaphase preparations from fibroblast cultures support this hypothesis. Teratogenesis Carcinog. Mutagen. 20:147-159, 2000.

Comparative aspects of contraceptive steroids: effects observed in rats

Current regulatory guidelines for testing contraceptive drugs in long-term rodent studies have established dosages based on multiples of the proposed human usage level. These multiples in rodents are 1-2, 10, and 50. The estrogen/progestogen ratio for most human contraceptive drugs ranges from 1/5 to 1/80. One of the biological endpoints in arriving at the human estrogen/progestogen ratio is the development of an endometrial decidualization response. The ratio necessary to achieve a similar uterine response in the rat is 1:10,000 to 1:20,000. Thus, dosages in the rodent, when based only on a multiple of the proposed human usage level, result in a highly estrogenic combination with estrogen being completely dominant. Continuously elevated estrogen in the rat is toxic to dopaminergic neurons in the hypothalamus which secrete prolactin inhibiting factor (PIF). Hyperplasia of pituitary lactotrophs occurs from both the direct stimulatory effect of estrogen and the uninhibited secretory activity of lactotrophs related to depressed PIF secretions. Prolactinomas result. Increased levels of prolactin lead to mammary gland stimulation and tumor development. Dosage levels for future rodent studies of contraceptive drugs should be based on pharmacokinetics, endocrine profiles, and biological endpoints rather than on multiples of the human usage level.

Oral contraceptives: significance of their effects in man and relationship to findings in animal models

Combination oral contraceptives have been available since 1960. They contain both an estrogen and a progestogen and have been studied extensively in both lower animals and humans and have been the subject of special regulatory requirements for toxicological and clinical studies. The initial oral contraceptives, by today's standards, contained very high levels of both hormones. There has been a continuous decrease in the dose of both the estrogen and the progestogen during the past quarter century, with continued maintenance of high degree of effectiveness. This decrease of dosage has been stimulated by findings from prospective clinical trials and retrospective case control trials. As additional information has been gained with oral contraceptives, new benefits beyond their effectiveness as contraceptives have been realized. Today's oral contraceptives provide a high degree of effectiveness, low incidence of nuisance side effects, and low incidence of major adverse effects.

The synthetic progestin norethindrone causes thyroid endocrine disruption in adult zebrafish

Synthetic progestin norethindrone (NET) widely used in oral contraceptives, hormonal therapy and livestock farming has been detected in various aquatic ecosystems. Recent studies have shown that NET can cause thyroid endocrine disruption in amphibians. However, studies are still lacking on thyroid axis of fish. In the present study, we investigated thyroid hormone levels (T3 and T4) and transcriptional patterns of 15 genes of the hypothalamic-pituitary-thyroid axis (HPT axis) in adult zebrafish that were exposed to solvent control and three measured concentrations of NET (7, 84 and 810 ng/L) for 90 days. The results indicated that NET significantly lowered T3 and T4 levels in both female and male zebrafish. Transcriptional expression profiles of some of the HPT-axis related genes were disrupted. Specifically, the expression levels of tshb and pax8 have increased significantly while dio2 and ugt1ab have decreased in females. In male, however, tshb expression levels were increased while ttr, ugt1ab, thra and thrb were decreased. The overall results demonstrate that NET disrupts thyroid endocrine system by interfering at multiple sites along HPT axis in adult zebrafish.

Pre-clinical evaluation of contraceptive steroids: regulatory requirements and scientific expectations

The development of new contraceptive steroids placed great pressures on regulatory agencies. There was insufficient time to develop a novel pre-clinical safety evaluation, hence their toxicity in animals was assessed as with other drugs. The approach of regulatory agencies to toxicity and carcinogenicity testing of these steroids are discussed and evaluated.

Effect of oral contraceptive steroid hormones on metabolic parameters of streptozotocin-induced diabetic rat

This study examined the effect of 0.05 mg norgestrel + 0.01 ethinyl estradiol (NEE) Kg x body wt(-1) on body weight, random blood glucose, glycosylated hemoglobin, and plasma insulin levels in streptozotocin-induced diabetic rats. Weight loss, blood glucose, glycosylated hemoglobin, and plasma insulin values of rats treated with NEE before and after the onset of diabetes were not significantly different from that of untreated diabetic rats. In conclusion, oral administration of these contraceptive steroid hormones does not significantly alter the metabolic parameters of diabetic rats.

A comparative study of two estrogen dosages in combined oral contraceptives among Sudanese women

A prospective study of two combined oral contraceptives was conducted in the Sudan. No pregnancies occurred. Overall incidence of side effects was low. Headache was most frequently reported. Elevations were observed for weight, systolic and diastolic blood pressures, and SGOT and SGPT values while a decrease was seen for hemoglobin levels. Menstrual irregularities were not a problem for the users. Total 6-month use discontinuation rates were low for both pill groups.

Globulines anormalment precipitables (GAP) in Nigerian users of progestogen-only pill

The globulines anormalment precipitables (GAP), which have been reported to be raised in current and former oral contraceptive users, were measured in Nigerian subjects which included male volunteers. The results showed that GAP were present in males who had never used contraceptives and that the mean values were lowest in intrauterine contraceptive device (IUD) users and highest in females who had never used any contraceptives. However, current contraceptive users had lower mean GAP values than either former users or never users. It was therefore concluded that GAP levels alone cannot be used to predict the development of thromboembolic complications in pill users, and that ethinyl estradiol cannot be the main physiological stimulus for GAP synthesis.

Enhancement of mutagenic activity in Salmonella by contraceptive steroids

Two oral contraceptive steroids, mestranol and norethynodrel, were evaluated for mutagenicity in the Salmonella histidine reversion assay. The pure forms of the hormones were not mutagenic when tested with either missense (TA1535, TA100) or frameshift (TA98, TA1538, TA1537) strains. In vitro activation of the hormones with liver homogenates from rats induced either with phenobarbital or Aroclor did not influence these results. However, mestranol was capable of enhancing the mutation yield obtained by an ineffective subthreshold dose of 2-acetylaminofluorene. Dimethyl sulfoxide extracts of two contraceptive pills, Ovulen-21 (containing mestranol) or Enovid-E (containing mestranol or norethynodrel), also were nonmutagenic. But again, both these extracts were capable of enhancing the mutation yield induced with an ineffective dosage of 2-acetylaminofluorene and N-nitrosopiperidine. These studies point to the possible promotional effect and subsequent potential hazard to the female consumers who use these hormones as a means of pregnancy control.

Effects of female sex steroids on concanavalin A-mediated agglutination of hepatocytes from nonregenerating and regenerating rat liver and hepatic tumor marker enzymes

Effect of treatment of female rats with an oral contraceptive agent (OCA), Ovulen-50, for 7 weeks on agglutination of hepatocytes with concanavalin A (con A) and activities of certain tumor marker enzymes were examined to find out if OCA treatment is related to preneoplastic or neoplastic processes. Hepatocytes from regenerating and nonregenerating livers of control female rats showed negligible agglutination with Con A, whereas hepatocytes from non regenerating but not from the regenerating livers of female rats treated with a combination of 5 micrograms ethinyl estradiol and 100 micrograms ethynodiol diacetate showed agglutination. Of the tumor marker enzymes such as hepatic glucose 6-phosphatase, gamma-glutamyl transpeptidase (gamma-GT), and arginase examined in the liver, only gamma-glutamyl transpeptidase showed a significant increase in activity in the steroid-treated rats. Plasma alkaline phosphatase activity was also higher in the treated animals. However, the magnitude of the changes observed was relatively small and perhaps unrelated to the neoplastic process.