Induction of micronuclei and of enzyme-altered foci in the liver of female rats exposed to progesterone and three synthetic progestins.

Progesterone (PG) and three structurally similar synthetic progestins-norethisterone (NE), allylestrenol (AE), and dydrogesterone (DG)-have been compared for their ability to induce the formation of micronuclei and of enzyme-altered foci in the liver of female rats. In the micronucleus assay, carried out in rats given a single p.o. dose of 100 mg kg-1 3 days before partial hepatectomy and sacrificed for cell sampling 2 days later, the frequency of micronucleated hepatocytes was 3.5-fold higher than in controls with PG, 2.8-fold with DG, 2.2-fold with NE and 2.1-fold with AE, but the increase was statistically significant only for PG. In the liver foci assay, performed to evaluate the tumor initiating activity of p. o. dosing with 100 mg kg-1 once a week for 6 successive weeks, the values of the number and area of gamma-glutamyltranspeptidase-positive foci were, as compared to controls, 15.9- and 100-fold higher with NE, and 13.9- and 52-fold higher with AE, but only the increase of area produced by NE was statistically significant; PG and DG did not display in this test any activities. Considered together with previous findings, these results suggest that NE might be biotransformed in the liver into reactive species and thus behave as a weak genotoxic agent.

Hormonal imprinting and damages caused by fetal steroid treatment. Influence of fetal treatment with pregnancy-protecting steroids (allylestrenol, diethylstilbestrol) on the effect of gonadotropin administered to cockerels perinatally and at the age of six weeks.

Single fetal (9th day) treatment with either diethylstilbestrol (DES) or allylestrenol (AE) caused a considerable decrease, both at the age of five days and six weeks, in the weight of the testicles and the diameter of the seminiferous cords, while the ratio of spermatogonia to primary spermatocytes increased. When measured either at the age of five days or six weeks, gonadotropin treatment [a combination of follicle stimulating hormone (FSH) and luteinizing hormone (LH)], administered twice daily for three days after the hatching, led to an increase in the above-mentioned parameter and to a shift in the cell ratio towards the control value. However, the absolute value of the controls treated with FSH-LH was by far not reached. The effect of perinatal treatment could be detected even in adulthood, namely, at the age of five days the response capability was relatively weak in the cockerels treated with DES and AE, while high responsiveness was observed at the age of six weeks. In some cases the relative value of the increment exceeded even that of the control; however in absolute term it was well below the control. On the basis of these experiments it might be concluded that hormonal imprinting evoked by FSH-LH treatment also occurs in the gonad damaged by DES and AE. The setting in of imprinting ameliorates the damages caused by DES and AE and increases the response capability of the cells.

Effect of embryonic and/or neonatal diethylstilbestrol and allylestrenol treatment on postnatal development of the chick testis.

The synthetic steroid diethylstilbestrol (DES) and the steroid-like allylestrenol (AE) have been used for years in human medicine for the protection of pregnancy. The hazards to the fetus of gestational DES treatment are well established [2, 17, 18]. Knowledge of a similar effect of AE is still fragmentary. Therefore, further studies are required of the after-effects of embryonic and perinatal AE exposure. In our earlier experiments with polypeptide hormones [4, 5, 6] we have observed that perinatal age is a critical period in the maturation of hormone receptors. In this period the presence of hormone induces the development of its specific receptors. The phenomenon is termed hormonal imprinting [4, 5, 6]. During its maturation the receptor is flexible and the presence of non-specific hormones capable of binding to it may alter its normal development Accordingly, even a single hormone injection in the perinatal period may alter the hormone-sensitivity of the target organ.

Influence of single neonatal treatment with allylestrenol or diethylstilbestrol on microsomal enzyme activity of rat liver in adulthood.

A single neonatal treatment of rats with a steroid (allylestrenol or diethylstilbestrol) did not alter the later activity of the hepatic microsomal (cytochrome P-450) enzyme system, but inhibited the inducer action of another steroid (testosterone) administered at the age of six weeks. This suggests that a hormonal imprinting-like mechanism also operates in the case of enzymes.

Late effects of embryonic allylestrenol treatment in chicken.

Allylestrenol when applied to chick embryos on the 9th day of incubation or on the 9th day of incubation and at hatching brought about a severe purulent inflammation of the oviduct at 6 weeks of age in 50% of the animals. Treatment at hatching only had no effect whatsoever. The findings suggest that allylestrenol must be applied with caution during pregnancy.

Influence of neonatal steroid (diethylstilbestrol, allylestrenol) treatment on the sexual behaviour of the adult rat.

A single neonatal treatment with diethylstilbestrol (DES) or allylestrenol (AE) considerably depressed the sexual activity of male rats in adulthood. DES had a stronger depressive effect than AE. Though the adult sexual activity of intact female rats was also reduced by DES it was not influenced by AE. Ovariectomized females that had been hormone-treated before experimental mating showed reduced sexual activity under the influence of neonatal DES-treatment but increased sexual activity when treated neonatally with AE.