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Biomedical subjects

V Hansson

Publications and source records attributed to V Hansson.

At least 181 records · Page 10Linked to original sources
PubMed1980

Physico-chemical characterization of the soluble 3 alpha-hydroxysteroid oxidoreductase in the rat testis and prostate.

The present paper describes some physiocochemical properties of the soluble 3 alpha-oxidoreductases in the rat testis and prostate, and comparison with rat epididymal 3 alpha-oxidoreductase, published previously (Hastings & Hansson 1979). The testicular enzyme shows properties very similar to that in the epididymis (size, stability, pH optium) except for minor differences in charge (iso-electric point). The prostatic enzyme revealed a slightly higher molecular weight, and was more sensitive to heating than those in the testis and epididymis, whereas the iso-electric point was the same as that in the testis (pI-5.25). The enzymes in all tissues exhibit very similar shapes (f/fo 1.14-1.17). The similar properties of the testicular and prostate 3 alpha-oxidoreductases to those previously reported for that in the epididymis may indicate that these enzymes represent identical peptide chains. The small differences observed in size, temperature stability and change may be due to their presence in different environments.

Animals↗
PubMed1980

PGE1 and hCG responsive adenylyl cyclases in interstitial cells from rat testis: biphasic effects of calcium.

The effects of PGE1 (10 micrograms/ml), hCG (10 mIU/ml) and Ca2+ (0-10 mM) on rat interstitial cell adenylyl cyclase (AC) activity have been investigated. Like hCG, PGE2 also stimulated membrane bound AC, and both hormonal effects proved to be influenced by Ca2+. Low concentrations of Ca2+ (0.3 mM) enhanced hormonal stimulation, while high concentrations (up to 10 mM) suppressed AC activity. Relative stimulations caused by PGE1 and hCG were maximal in the presence of 0.6 mM Ca2+. Ovine FSH (NIH-S12), at concentrations causing maximal activation of AC in seminiferous tubules (12.5 micrograms/ml), had no effect on AC in interstitial cells. Germinal cell membranes displayed insignificant AC activity. We therefore conclude that the AC activity stimulable by PGE1 is located on Leydig cell membranes and that both PGE1 and hCG activities are susceptible to regulation by Ca2+.

Adenylyl Cyclases↗
PubMed1980

Mn2+-dependent adenylyl cyclase (AC) in rat testis: kinetic properties and optimalization of assay conditions.

The aim of the present study was to investigate some kinetic properties of the soluble Mn2+-dependent adenylyl cyclase (AC) in rat testis and to examine the viability of this enzyme under various assay conditions. 1. Constant AC activity was found during the first 35 min of incubation, and AC activity was proportional to protein concentrations in the range tested (10-45 micrograms/tube). 2. The enzyme activity was constant for at least 24 h at 4 degrees C and for at least 2 h at 35 degrees C. At higher temperatures (above 45 degrees C) the AC activity rapidly declines. 3. The enzyme displays a pH optimum in the physiological range (7.0-7.4) and increasing ionic strength (0-0.4 m NaCl/KCl) caused only a marginal decrease in enzyme activity. 5. The soluble Mn2+-dependent AC in rat testis could not be stimulated by hormones (hCG, FSH, prostaglandins), guanyl-nucleotides (GMP-P(NH)P, 2-4 x 10(-5) M) or F-. Ca2+ (0.1-5 mM) caused a dose-dependent stimulation of AC activity; the most pronounced effect was seen at low Mn2+ concentrations. 6. The Km for MnATP2- was estimated to 3.0 mM and the Km for Mn2+ to 7.2 mM. Increasing concentrations of Mn2+ did not alter the affinity for MnATP2- and neither did varying levels of ATP affect the affinity for Mn2+.

Adenosine Triphosphate↗
PubMed1980

LH/hCG responsive adenylyl cyclase in rat testis and testes from testicular feminized male (Tfm) rats and mice; desensitization by homologous hormone.

Testes of testicular feminized (tfm) rats and mice, as well as of normal male rats contain an LH/hCG responsive adenylyl cyclase. Basal, as well as hCG stimulated activities were higher in tfm rats and mice than in normal rats. The presence of an LH/hCG responsive adenylyl cyclase in the testis of tfm rats and mice shows that the greatly elevated LH levels present in males having this syndrome, giving 80-90% reduction in LH/hCG receptors, do not cause an uncoupling of the remaining receptors from the adenylyl cyclase. It also shows that androgens are not essential for coupling of the LH/hCG receptors to the adenylyl cyclase. Injection of 200 IU of hCG into adult normal rats and tfm rats caused, after 48 h, a complete loss of LH/hCG stimulated adenylyl cyclase whereas the FSH responsive adenylyl cyclase in both animal preparations was maintained. Desensitization of the LH responsive adenylyl cyclase by hCG in normal rats, confirms previous studies showing lack of hCG stimulated cyclic-AMP secretion after a comparable dose of hCG in vivo. Similarly, hCG (50 IU) caused a transient loss of LH/hCG responsive adenylyl cyclase in tfm mice, with a complete disappearance of response after 24 h. At 48 and 72 h after injection of hCG the response gradually returned to normal. The fact that hCG caused a complete desensitization of the LH/hCG responsive adenylyl cyclase in both tfm rats and mice, proves that androgen receptor mediated events are not involved in hCG desensitization of the adenylyl cyclase in Leydig cells.

Adenylyl Cyclases↗
PubMed1980

Calmodulin regulation of testicular cyclic nucleotide phosphodiesterases.

Three different, calmodulin-dependent, isoenzymes of cyclic nucleotide phosphodiesterase (PDE) can be isolated by DEAE cellulose chromatography from the immature rat testis and shown to have different substrate specificities and kinetic behaviour. Calmodulin is regulating the activity of these enzymes by altering the maximal velocity (Vmax) rather than the Km of the reaction. Two of the 3 enzymes appear to be testis-specific, while the remaining possesses properties similar to that described for the calmodulin-dependent PDE found in other tissue.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1980

Cofactor dependency of soluble 3 alpha-hydroxysteroid oxidoreductases in rat testis, prostate, and epididymis.

The present paper demonstrates the presence of at least two 3-hydroxysteroid oxidoreductases (3-HSO) in rat testis, prostate, and epididymis cytosol preparations. The enzymes were either NADH or NDAPH dependent. Further investigation by Sephadex G-200 chromatogrphy revealed the presence of enzyme activities in the void volume (peak 1) and also eluting close to the methyl-carbonic anhydrase standard (mol wt, 34,000; peak 2). Enzyme activity in peak 1 was predominantly stimulated by NADH and that in peak 2 was stimulated mainly by NADPH. Both 3 alpha- and 3 beta-HSO activities were observed in testicular eluates from 1; 3 beta-Adiol accounted for up to 50% of the 5 alpha-androstanediols formed. In peak 2,3 alpha-HSO constituted more than 90% of the enzyme activity. In contrast, the prostatic and epididymal eluates revealed only 3 alpha-HSO activity; 3 beta-Adiol constituted less than 5% of the 5 alpha-androstanediols formed in either peak 1 or 2. The apparent Km values for enzyme activation reveal differences in sensitivity to cofactors for enzymes in peaks 1 and 2 and also among testis, epididymis, and prostate. NADH caused a very similar activation of enzyme activity in peak 1 or the prostate and epididymis (Km 50-100 micro M), whereas the enzyme in the testis was activated by much lower cofactor concentration (Km approximately 5 microM). It is possible that this enzyme activity may represent microsomal contamination. The enzyme activity in peak 2 revealed very similar sensitivity to NADPH in all three organs (Km, 0.6-1.7 microM), confirming previous studies from our laboratory that the soluble. NADPH-dependent enzymes in all three tissues are very similar, if not identical.

3-Hydroxysteroid Dehydrogenases↗
PubMed1980

FSH-response adenylyl cyclase in rat testes: desensitization by homologous hormone.

Injection of high doses of FSH causes a partial desensitization of the FSH-responsive adenylyl cyclase (AC) in adult rat testes. The loss of responsiveness to FSH is dependent on time. Two hours after injection of one dose of human FSH (256 micrograms hFSH-PT2) in vivo, no effect was seen on FSH-stimulated AC activity (Km and maximal activation). After 24 hr there was an approximately 40% decrease in FSH activated AC. Injection of two doses of FSH (256 micrograms hFSH-PT2) 24 and 48 hr before being killed, gave a loss in FSH-responsive AC activity of approximately 60%. The decreased FSH-stimulated AC activity after FSH injections in vivo was associated with a comparable decrease in specific FSH binding. Whether this is a reflection of receptor occupancy or down regulation of the number of FSH receptors is not known. Desensitization of the FSH-responsive AC caused by FSH was not associated with a change in its Km.

Adenylyl Cyclases↗
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↗