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Biomedical subjects

K Purvis

Publications and source records attributed to K Purvis.

At least 109 records · Page 6Linked to original sources
PubMed1979

LH contamination may explain FSH effects on rat Leydig cells.

Treatment of immature, hypophysectomized male rats with 50 micrograms ovine FSH (NIH-FSH-S12) twice a day for 5 days stimulated the maximum quantity of 17 beta-hydroxyandrogen produced by isolated Leydig cells in response to hCG. Pretreatment of the FSH preparation with an LH antiserum in one study markedly reduced and in another study completely abolished this stimulatory effect of FSH, but only slightly impaired the capacity of the hormone to stimulate the Sertoli cell in vivo (epididymal androgen-binding protein). Administration of another highly potent FSH preparation (LER-1881) had no discernible effects on the dose-response characteristics of the Leydig cells but was superior to the NIH-FSH-S12 in its capacity for stimulating the Sertoli cell. When all hormone preparations were tested for their ability to stimulate steroid secretion from normal Leydig cells in vitro, a close correlation was obtained between their Leydig cell-stimulating activity (a measure of LH contamination) and their capacity to alter Leydig cell responsiveness after in-vivo treatment. FSH treatment had no effects on specific LH binding per 10(6) Leydig cells. It is concluded that the stimulatory influence of FSH on rat Leydig cells may to some extent be a result of the LH contaminating the hormone preparation.

Androgens↗
PubMed1979

Endocrine correlates of meiosis in the male rat.

Changes in the proportion of cells within various DNA classes of dispersed testicular cells from the developing rat were monitored by microflow fluorometry and correlated with changes in the function of the pituitary (FSH), of the Leydig cells (androgens) and Sertoli cells (androgen-binding proteins, ABP). Peaks of androgens and of FSH appeared simultaneously and coincided with an accumulation of tetraploid cells and with the first appearance of haploid cells in the testis and ABP in the epididymis. Estrogen treatment (5 micrograms/day) of developing rats from day 7 completely prevented the appearance of haploid cells in the testis as well as ABP in the epididymis. In these animals the wave of tetraploid cells started and progressed normally, indicating that transformation and progression of germinal cells to the stage of the primary spermatocytes were taking place. A combined treatment with FSH and dihydrotestosterone propionate (DHTP) resulted in a premature start of Sertoli cell secretion of ABP into the epididymis, but in a normal appearance of haploid and tetraploid cells. The time correlation between peaks in FSH/androgens, the start of Sertoli cell secretion, and the occurrence of haploid cells in the testis stresses the importance of these two hormones for normal Sertoli cell function and the importance of a functional Sertoli cell for the completion of meiosis.

Aging↗
PubMed1979

Prolactin and Leydig cell responsiveness to LH/hCG in the rat.

The effects of prolactin and 2-bromo-alpha-ergocryptine (CB-154) on Leydig cell function in intact and hypophysectomized male rats were studied. The conclusions can be summarized as follows: prolactin (1) has a direct stimulatory effect on the number of LH receptors on rat Leydig cells, (2) has no effect on the characteristics of the dose-response curve of isolated Leydig cells (hCG stimulated androgen production) in vitro even after treatment with pharmacological doses in vivo, and (3) acts synergistically with LH to stimulate the quantity of androgen produced by the Leydig cells in response to hCG in vitro and to increase the sensitivity of the hCG-dose-response curve. Treatment of intact rats with CB-154 reduced the quantity of androgen produced by the Leydig cells in vitro after exposure to hCG and decreased LH binding to the same cells by 50%. These results suggest that under normal conditions, endogenous prolactin plays a key role in maintaining the functional integrity of rat Leydig cells.

Animals↗
PubMed1978

Decreased Leydig cell responsiveness in the testicular feminized male rat.

The Stanley-Gumbreck pseudohermaphrodite or testicular feminized male (tfm) rat exhibits a decreased Leydig cell sensitivity to human CG (hCG) measured by androgen and cyclic-3',5',-adenosine monophosphate production in vitro. These changes were associated with an 80% reduction in the number of LH receptors in the tfm testis, when compared on the basis of equivalent amounts of testis particle protein or per 10(6) isolated Leydig cells. Androstenedione and not testosterone is the major androgen secreted by the tfm Leydig cell and androstenedione secretion is, therefore, a more appropriate end point than testosterone secretion for Leydig cell function in tfm animals. A dose of hCG (3 ng/2 ml) which elicited a near maximal response in androgen production from the decapsulated testes and Leydig cell suspensions of normals rats, did not significantly stimulate androgen production from Leydig cells of the tfm animals. A much higher dose of hCG (200 ng/2 ml) gave a response from the tfm Leydig cells which was comparable to that obtained with 3 ng from Leydig cells of normal littermates. This indicates that the small number of LH receptors on the tfm Leydig cell membrane are functional and that the reduction in receptor number results in a decrease in the sensitivity of response to LH rather than a reduction in the maximum steroid response.

Androgen-Insensitivity Syndrome↗
PubMed1978

Androgens and androgen-binding protein in the rat epididymis.

The levels of testosterone, dihydrotestosterone (DHT), 5alpha-androstan-3alpha,17beta-diol and androgen-binding protein (ABP) were measured in various segments of the epididymis from adult rats which had been unilaterally orchidectomized for 4 weeks. On the 'intact' side, ABP concentrations were highest in the caput region. The segmental distribution of DHT closely followed that of ABP with the highest concentration in the caput (40 ng/g tissue) and lowest in the cauda (10 ng/g tissue) epididymidis. There was a high degree of correlation (r = 0.98) between the concentration of DHT in the epididymis and ABP levels. 'Castration' completely abolished the DHT gradient. The levels of testosterone and androstanediol were lower than those of DHT; most was present in the corpus epididymidis. The relative differences were reduced after 'castration'. It is concluded that ABP in the rat epididymis is the primary factor for determining the concentration of DHT in the epididymal fluid.

Androgens↗
PubMed1978

Age-related changes in responsiveness of rat Leydig cells to hCG.

The responsiveness of decapsulated testes and isolated Leydig cell preparations from rats (30-80 days of age) to a constant dose of 3 ng hCG/2 ml was assessed by comparison of the production of testosterone and "total 17beta-hydroxy androgen" (17beta-HA). When testosterone secretion was used as the index of response, there was a marked increase in the production with age by decapsulated testes and also by equal numbers of Leydig cells. When 17beta-HA was taken as the response parameter this increase was only marginal for the decapsulated testes and there was an age-dependent decrease when expressed per 10(6) cells. These differences probably reflect changes in the metabolism of testosterone to 5alpha-reduced products with increasing age because 80% of androgen secreted at 30 days is 3alpha-androstanediol and 86% is secreted as testosterone at 80 days. We conclude that for studies on hCG responsiveness and the steroidogenic capacity of immature rat Leydig cells (a) testosterone is an inappropriate response parameter and (b) this response undergoes a decrease rather than an increase during prepubertal development.

Aging↗
PubMed1978

Carnitine levels in human accessory sex organs.

Carnitine concentration was measured in human tissue obtained at surgery or autopsy. In all patients, the concentration of carnitine (nMol. g-1 tissue) was higher in epididymis than in testis, vas deferens, prostate, and seminal vesicles. There was no correlation between the tissue levels of testosterone in the testis and the concentration of carnitine in epididymis. As in the rat and baboon, carnitine is also found in high concentrations in the human epididymis.

Adolescent↗