Treatment Of Immature Female Rats Research Articles

Fenvalerate, A Pyrethroid Insecticide, Adversely Affects Sperm Production and Storage in Male Rats

The aim of this study was to investigate the potential estrogenic activity of fenvalerate by examining reproductive and fertility capabilities in Wistar rats. Adult male animals were treated for 30 d with 20 or 40 mg/kg/d fenvalerate or corn oil (vehicle) by oral gavage. Further, a possible estrogenic activity of fenvalerate (0.4, 1, 4, 8, or 40 mg/kg) was tested after a 3-d treatment of immature female rats using the uterotrophic assay. Exposure to the higher dose of fenvalerate was toxic to testis and epididymis as shown by a decrease in the absolute weights and sperm counts in both organs. Although the sperm counts were reduced, the fertility and sexual behavior were similar in control rats and rats treated with 40 mg/kg pesticide. Fenvalerate did not exert estrogenic activity in vivo at the tested doses. Data suggest that fenvalerate treatment in this study failed to compromise fertility, possibly due to enhanced reproductive capacity in rodents compared to humans.

Reproductive evaluation of aqueous crude extract of Achillea millefolium L. (Asteraceae) in Wistar rats

The present study was conducted to evaluate the toxicity of the exposure to the aqueous extract from leaves (AE) of Achillea millefolium L. on reproductive endpoints in Wistar rats. Adult male rats were treated daily with yarrow extract (0.3, 0.6 and 1.2 g/kg/day) during 90 days by oral gavage. Endpoints including reproductive organ weights, sperm and spermatid numbers as well as sperm morphology were evaluated. No clinical signs of toxicity were detected over the treatment period, and body weight gain was similar in all groups. A significant increase in the percentage of abnormal sperm in the group treated with the highest dose of yarrow extract was detected with no other important changes in the other reproductive endpoints studied in the male rats. Furthermore, a possible estrogenic/antiestrogenic activity of the yarrow extract screened after a 3-day treatment of immature female rats which did not show any uterotrophic effects.

Effects of female sex hormones on polyamine-oxidizing enzyme activities and polyamine concentrations in immature rat uterus and liver.

17 beta-estradiol (E2) and progesterone (P) treatment of immature female rats (10 micrograms/100 g body weight) respectively resulted in 1.38-fold (p < 0.02) and 1.42-fold (p < 0.02) increase in the uterine polyamine oxidase activity, and 2.45-fold (p < 0.001) and 1.43-fold (p < 0.02) increase in the uterine diamine oxidase activity, as compared to the controls. E2 caused a 5-fold (p < 0.05) and a 1.36-fold (p < 0.05) increase in putrescine and spermidine concentration respectively in rat uterus. Increases of 1.7-fold (p < 0.02) and 1.6-fold (p < 0.05) in putrescine and spermine concentration were determined in the P-treated uterus, as compared to the controls. The spermidine/spermine ratio, which is regarded as an index of growth rate, was higher in the E2-treated uterus and lower in the P-treated uterus than in the control uterus. No statistically significant hormonal effects were estimated in the immature liver. The data reported suggest the possibility of an involvement of polyamine-oxidizing enzymes in the modulation of polyamine concentrations in rat uterus by the female sex hormones.

Estrogen regulates expression of the jun family of protooncogenes in the uterus

Treatment of immature female rats with estradiol increases uterine levels of c- jun and jun-B mRNAs approx. 10-fold. This effect is specific for estrogenic steroids. The induction of jun transcripts is blocked by actinomycin D but not puromycin, suggesting that the hormonal effect is due at least in part to transcriptional activation. The hormone effect is rapid and peak levels of jun mRNAs are seen within 3 h after treatment. Inductions of jun and fos transcripts in the uterus by estradiol exhibit similar dose response curves (maximum responses at 4 μg/kg). Estradiol also elevates uterine levels of jun-D, and this induction is insensitive to puromycin. In vivo treatment with the phorbol ester TPA rapidly elevates uterine levels of fos, jun, and myc transcripts, indicating that expression of these photooncogenes is under non-estrogenic as well as estrogenic regulation in this target tissue. These results suggest that multiple members of the jun and fos protooncogene families may play a role in amplifying the uterine response to estrogens.

Peripubertal Treatment with N-Methyl-D-Aspartic Acid or Neonatally with Monosodium Glutamate Accelerates Sexual Maturation in Female Rats, an Effect Reversed by MK-801

Recent reports from several laboratories have implicated the excitatory neurotransmitter glutamate as a component in the neural regulation of sexual maturation. In the rat we have previously proposed that a hypothalamic opioid restraint mechanism may ultimately be overridden by maturation of an excitatory drive, culminating in first ovulation. We have now investigated whether glutamate may be the excitatory factor. Treatment of immature female rats with single, daily injections of two N-methyl-D-aspartate (NMDA) antagonists--dextrorphan (18 mg/kg) and MK-801 (0.1 mg/kg)--beginning on the 27th postnatal day, significantly delayed the timing of vaginal opening (VO). Interestingly, treated rats reached VO in spite of continued antagonist treatment. The antagonist effect was reversed by preinjection of NMDA, suggesting that endogenous glutamate exerts its effect via an NMDA-subtype glutamate receptor. Injection of NMDA alone (15 mg/kg; once daily) produced a striking synchronization of VO such that all treated rats showed VO over a 24-hour period compared to a normal distribution of several days for control rats. In a model of first ovulation, i.e., rats induced to ovulate by pregnant mare serum, MK-801 (1 mg/kg) arrested treated rats at proestrus. This was readily reversible after discontinuing injections. A lower dose of MK-801 (0.1 mg/kg/day) was ineffective in delaying ovulation. In a second series of experiments we studied the consequences of a neonatal hypothalamic lesion which destroys glutamate-sensitive neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunohistochemical localization of tissue-type plasminogen activator in ovaries before and after induced and spontaneous ovulation in the rat

The observation that tissue-type plasminogen activator (tPA) activity increased dramatically in preovulatory follicles has led to the hypothesis that plasminogen activation is causally related to follicle rupture. With immunohistochemistry, we have studied the appearance of tPA in ovaries of immature rats induced to ovulate and in adult cycling rats. Treatment of immature female rats with a single dose of pregnant mare serum gonadotropin (PMSG) induced follicular maturation. A subsequent human chorionic gonadotropin (hCG) injection resulted in follicle rupture 12-14 h later. PMSG treatment alone did not induce appearance of tPA-immunoreactive cells in any ovarian compartment. After hCG stimulation, however, theca cells, granulosa cells, and oocytes of pre- and postovulatory follicles displayed distinct tPA immunoreactivity. Fibroblast-like cells in the theca layers and tunica albuginea of the follicle apex also demonstrated localized cytoplasmic tPA reactivity. In addition to tPA synthesis in preovulatory follicles, hCG also induced tPA staining in the theca (but not granulosa) layers of non-ovulatory follicles. At 24 h after hCG treatment, there was a marked tPA staining in developing corpora lutea, ovulated ova, and oviductal epithelium. Ovaries from regularly cycling adult rats displayed a similar ovulation-related pattern of tPA immunostaining. The appearance of tPA in different cell types of the preovulatory follicle and in the fibroblast-like cells at the follicle apex, strengthens the hypothesis of a direct involvement of tPA in follicle rupture. Presence of tPA in postovulatory oocytes, cumulus cells, and surrounding oviductal epithelium may also indicate a role for tPA in the transfer of eggs in the oviduct.

2-bromo-alpha-ergocryptine mesylate (CB-154) inhibits prolactin and luteinizing hormone secretion in the prepubertal female rat.

Treatment of immature female rats with 100 micrograms 2-bromo-alpha-ergocryptine mesylate (CB-154) per ml drinking water beginning on Day 30 of age until vaginal opening delayed puberty by 6 days. Rats treated with CB-154 exhibited vaginal opening at 43.3 +/- 0.6 days whereas controls exhibited vaginal opening at 37.9 +/- 0.8 days. Most interestingly, serum levels of luteinizing hormone (LH) and prolactin (PRL) on Days 31-35, determined by a homologous radioimmunoassay were significantly lower in treated rats than in controls. The ovarian concentrations of progesterone (P) and androstenedione (A) were lower in rats treated with CB-154 than in controls; ovarian estradiol (E2) concentrations were low in both groups. Serum levels of P (but not A and E2) were reduced on Days 31-35 of the treatment period. Cessation of the CB-154 treatment on the morning of Day 35 returned the onset of puberty to normal values; steroid and gonadotropin levels also returned to normal values within 2 days after removal of the CB-154 from the drinking water. Near the time of onset of puberty, serum levels of LH in rats treated with CB-154 returned to control values. These data indicate that in the female rat the delay in puberty induced by CB-154 might be due to a reduction in the secretion of LH, especially since the onset of delayed puberty in rats treated with CB-154 correlates with an increase in the serum level of LH. Further studies are needed to elucidate the specific effects of hypoprolactinemia on ovarian function and the onset of puberty in the rat.

Estrogen-induced prolactin and DNA synthesis in immature female rat pituitaries

Estradiol is likely involved in stimulating developmental changes in the ability of the rat pituitary to secrete prolactin. To investigate the possibility that these changes involve proliferation of prolactin cells, estradiol effects on pituitary growth and prolactin synthesis were examined. Estradiol treatment of immature female rats stimulates increases in pituitary weight, [ 3H]thymidine incorporation, DNA content and prolactin synthesis. Treatment of rats with the DNA synthesis inhibitor, hydroxyurea, partially blocked the ability of estradiol to stimulate prolactin synthesis suggesting that at least part of the effect of estrogen is due to cell proliferation. These results suggest that estrogen-induced proliferation of prolactin cells is involved in the developmental processes of the pituitary.

Estrogen-induced metabolism of estradiol-17 β in the rat uterus: A possible mechanism for the termination of estrogen action

Treatment of immature female rats with estrogen resulted in the induction of a peroxidase in the uterus which is able to convert estradiol-4- 14C to water-soluble products in vitro. It is suggested that this reaction may be part of an adaptive response to limit the duration of action of estradiol-17 β upon its target tissue.

Effect of halogenated hydrocarbon insecticides on the metabolism and uterotropic action of estrogens in rats and mice

Treatment of immature female rats with chlordane, dieldrin, heptachlor, lindane, p,p′-DDD, p,p′-DDE, or toxaphene for 7 days stimulated the metabolism of estrone by liver microsomal enzymes and inhibited the increase in uterine wet weight caused by estrone. The daily administration of as little as 2–5 mg/kg of chlordane ip for 7 days reduced the uterotropic action of tritiated estrone and decreased the concentration of tritiated estrogen in the uterus. The total body metabolism of tritiated estrone was enhanced in rats pretreated with 10 or 50 mg/kg of chlordane daily for 7 days. Treatment of adult ovariectomized mice with 25 mg/kg of chlordane once a week for 3 wk increased the metabolism of estradiol-17β by liver microsomal enzymes, reduced the estradiol-17β- or estrone-induced increases in uterine wet weight and decreased the amount of tritiated estrogen found in the uterus after injection of tritiated estradiol-17β or estrone. The administration of 25 mg/kg of p,p′-DDD to mice once a week for 3 wk failed to increase the metabolism of estradiol-17β by liver microsomal enzymes and did not affect the increase in uterine wet weight caused by estradiol-17β or estrone. A decrease in reproductive success was observed when female mice were treated with 25 mg/kg of chlordane once a week for 3 wk.

Estrogenic action of DDT and its analogs

The intraperitoneal injection of 50 mg/kg of purified o,p′-DDT, technical grade DDT, purified methoxychlor, or purified p,p′-DDT increased the uterine wet weight by 49, 43, 37, and 28%, respectively, 6 hours after injection. o,p′-DDD, m,p′-DDD, p,p′-DDD, and p,p′-DDE exhibited little or no activity. The intraperitoneal injection of as little as 5 mg/kg or 1 mg/kg of technical grade DDT or o,p′-DDT, respectively, caused a significant increase in the uterine wet weight in immature female rats. The injection of technical grade DDT or o,p′-DDT into ovariectomized adult rats also increased uterine wet weight, indicating that the effect of the DDT analogs was not mediated through the ovaries. Treatment of immature female rats with a 50 mg/kg injection of technical grade DDT or purified o,p′-DDT caused a severalfold stimulation in the incorporation in vitro of glucose-U- 14C into lipid, protein, RNA, and acid-soluble constituents in the uterus 6 hours after the dose of DDT. A smaller stimulatory effect was observed with purified p,p′-DDT. Treatment of rats with technical grade DDT, purified o,p′-DDT, methoxychlor or p,p′-DDT 2 hours before an injection of estradiol-17β-6,7- 3H inhibited the uptake of estradiol-17β-6,7- 3H by the uterus in vivo, possibly by competing for sites that bind estradiol-17β in the uterus. o,p′-DDD, p,p′-DDD, m,p′-DDD and p,p′-DDE did not inhibit the uptake of estradiol-17β-6,7- 3H by the uterus. Pretreatment of rats with carbon tetrachloride inhibited the uterotropic action of o,p′-DDT and technical grade DDT. This suggests the possibility that the action of these substances on the uterus may depend on the conversion of the analogs of DDT to estrogenic metabolites.

Decreased uterotropic potency of oral contraceptives in rats pretreated with phenobarbital.

Treatment of immature female rats with phenobarbital for 4 days inhibits the uterotropic action of synthetic estrogens such as ethynyl estradiol, ethynyl estradiol-3-methyl ether (mestranol) and diethylstilbestrol. Treatment of rats with as little as 0.25 mg of phenobarbital/kg twice daily for 4 days causes a 33% inhibition in the uterotropic action of a 1 μg oral dose of ethynyl estradiol-3-methyl ether. The inhibitory effect of phenobarbital administration on the action of diethylstilbestrol-3H is paralleled by decreased radioactivity in the uterus and by increased levels of NADPH-dependent enzymes in liver microsomes that metabolize diethyl-stilbestrol. Studies on the estrogenic activity of synthetic progestational steroids in rats revealed that the administration of norethindrone and norethynodrel increases the uterine wet weight and this effect is inhibited by pretreatment with phenobarbital. (Endocrinology 83: 149, 1968)

Effect of chronic phenobarbital treatment on the liver microsomal metabolism and uterotropic action of 17-beta-estradiol.

Treatment of immature female rats with phenobarbital (37 mg/kg, ip, twice daily) for 3 days increases the activity of liver microsomal enzymes that metabolize 17β-estradiol. The stimulatory effect of chronic phenobarbital administration on in vitro estradiol metabolism is paralleled in vivo by a blockade in the estradiol-induced increase in uterine wet weight and the incorporation of glycine-14C into uterine protein. However, a single dose of phenobarbital (45 mg/kg, ip), given 1 hr before the estrogen, does not inhibit estradiol-induced increases in uterine wet weight. The inhibitory action of chronic phenobarbital treatment on the increase in uterine wet weight caused by estradiol is not prevented by adrenalectomy or hypophysectomy, indicating that phenobarbital does not act through the pituitary-adrenal axis. (Endocrinology 80:135,1967)