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  • Author: ANANT P. LABHSETWAR x
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ANANT P. LABHSETWAR

Summary.

Prostaglandin F induced degeneration of embryos in intact pregnant rats but not in ovariectomized rats maintained on progesterone. The pituitary lh stores in the intact, treated rats were significantly higher than those in the pregnant, pseudopregnant or cyclic controls. The prostaglandin failed to inhibit the ovulatory release of lh in the cyclic rat. It is suggested that the luteolytic effect of PGF may be mediated in part by the increased synthesis and secretion of lh.

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ANANT P. LABHSETWAR

Summary.

Chlormadinone, a very potent synthetic progestagen, was administered subcutaneously for 10 days (400 μg/day) to intact, unilaterally and bilaterally spayed rats, either adult or immature, and pituitary levels of fsh (hcg augmentation method of Steelman & Pohley, 1953) and lh (oaad method of Parlow, 1958) were determined. The chlormadinone treatment induced a significant atrophy of the ovaries as well as ovarian interstitial tissue and a total blockade of ovarian compensatory hypertrophy in the unilaterally spayed rats. The pituitary concentration μg/mg) and the total content (μg/gland) of both lh and fsh were significantly increased by chlormadinone treatment of the intact and unilaterally spayed rats despite a significant atrophy of the pituitary gland due to treatment. In the bilaterally spayed adult and immature rats, chlormadinone did not alter the ovariectomy-induced rise in lh and fsh stores of the pituitary gland.

These results suggest that chlormadinone, when administered for 10 days in the dosages employed, induces storage of fsh and lh in the pituitary gland primarily by impairing the release of these hormones, without exerting any detectable inhibitory effects on their synthesis.

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ANANT P. LABHSETWAR

Summary.

Pituitary levels of fsh (Steelman-Pohley assay) and lh (Parlow assay) were determined in male rats of various ages. The lh level began to rise by Day 33 of life, reached a peak between Days 43 and 47, and declined in the post-puberal period.

The fsh level (μg/mg and μg/pituitary/100 g body weight) began to rise very much earlier and had already reached its peak around Day 33, when testicular growth was rapid but before full spermatogenesis was established. In post-puberal rats, the fsh levels were much lower than those reached before puberty.

The implication of these findings and the possibility that fsh and lh are sequentially involved in initiating spermatogenesis in the puberal rat are discussed.

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ANANT P. LABHSETWAR

Summary.

Pituitary lh content was compared in pregnant rats in which implantation of blastocysts was successfully delayed for 9 to 12 days by three different methods. Both the concentration (μg/mg) and total content (μg/gland) of lh were low during lactational and Provera-induced delayed implantation periods but were high in bilaterally-spayed progesterone-treated rats when compared to cyclic control animals.

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ANANT P. LABHSETWAR

Summary.

The serum levels of lh were measured by radioimmunoassay in androgen-sterilized and normal cyclic rats, both in the presence and absence of ovaries. The serum of persistent-oestrous rats contained significantly more lh than that of normal rats on the day of oestrus, the raised level being comparable to that found in the adult male rat. The pituitary gland of the persistent-oestrus rat resembled that of the normal rat in its response to ovariectomy by increased secretion of lh.

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ANANT P. LABHSETWAR

Summary.

The pituitary contents of fsh (hcg augmentation method of Steelman & Pohley) and lh (ovarian ascorbic acid depletion method of Parlow) were determined at 0, 2, 9, 13 and 25 weeks and at 0, 2 and 13 weeks, respectively, after bilateral spaying. The fsh concentration (μg/mg) increased up to 9 weeks with no changes thereafter, but the fsh content (μg/gland) and also lh levels increased up to 13 weeks.

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ANANT P. LABHSETWAR

Summary.

Hypophysial levels of fsh (hcg augmentation method) and lh (ovarian ascorbic acid depletion method) were compared in pseudopregnant and in pseudopregnant-hysterectomized rats on Days 7 and 8 of pseudopregnancy. Hysterectomy failed to affect significantly the hypophysial levels of both gonadotrophins during the period studied.

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ANANT P. LABHSETWAR

Summary.

In an attempt to characterize the effects of medroxyprogesterone (17α-acetoxy-6α-methyl progesterone) more precisely, the compound was administered subcutaneously to immature rats twice a week (12·5 mg/injection) for 5 weeks. The effects of medroxyprogesterone on the pituitary gland were evaluated by measuring the lh content of the gland by the method of Parlow, while those on the ovaries were studied by measuring the ovarian response to exogenous pms (10 i.u.). In the treated animals there were significant decreases in ovarian, uterine, adrenal, pituitary and body weights; corpora lutea were absent and vaginal opening was delayed. The ovarian response to pms was not decreased. There was a significant decline in both concentration and total gland content of lh due to treatment.

It is suggested that the major action of medroxyprogesterone, when administered for an extended period of time in the doses used, is exerted at the pituitary level. It blocks the synthesis of LH in the pituitary gland without affecting ovarian sensitivity to gonadotrophins.

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ANANT P. LABHSETWAR

Summary.

The effects on the pituitary lh levels of norethynodrel (20 μg/rat or approximately 0·1 mg/kg daily) and mestranol (1 μg/rat or approximately 5 μg/kg daily) administered subcutaneously singly or in combination for 10 days to intact female rats have been studied. lh was assayed by the ovarian ascorbic acid depletion method of Parlow (1958). Norethynodrel caused a significant increase in hypophysial lh stores without causing ovarian atrophy or reducing compensatory hypertrophy in unilaterally ovariectomized post-pubertal rats. Mestranol administration, on the other hand, resulted in a significant ovarian atrophy without significant changes in the pituitary lh level, and also resulted in an inhibition of compensatory hypertrophy. The combined treatment resulted in effects essentially similar to those observed in the mestranoltreated group. No evidence for potentiation between the two steroids was obtained.

Data support the conclusion that when the two steroids are administered together in the dosages used, the oestrogenic component is primarily involved in the pituitary lh inhibition.

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ANANT P. LABHSETWAR and ALLEN C. ENDERS

Summary.

The progesterone content of corpora lutea from armadillos in the delayed implantation period and both corpora and placentae from animals in the post-implantation period was determined chemically.

During the delay period the weight of the corpus luteum, but not the total progesterone content (μg/gland), was significantly higher in animals carrying blastocysts than animals without blastocysts. Following implantation of the blastocyst, the size as well as the total progesterone content increased significantly (P<0·05). However, during the latter part of the post-implantation period (> 6 cm crown-rump length) both the size and the progesterone content decreased by more than two-fold (P<0·05). However, at this stage considerable amounts of progesterone were found in placentae and in one uterine vein blood sample studied. In contrast, no hormone could be detected in the placenta of earlier stages (i.e. <5 cm crown-rump length).

These data suggest that the functional activity of the corpus luteum may be lower during delayed implantation than in the early post-implantation period. However, during the latter part of gestation the corpus luteum regresses, and it is probable that at this stage the placenta contributes significant amounts of progesterone.