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Biomedical subjects

F F Rommerts

Publications and source records attributed to F F Rommerts.

At least 91 records · Page 5Linked to original sources
PubMed1983

The role of phosphoproteins and newly synthesized proteins in the hormonal regulation of steroidogenesis in Leydig cells.

LH activation of steroidogenesis in Leydig cells is accompanied by increased phosphorylation of at least 5 phosphoproteins. The 17000 Da protein is localized in nuclei and appears not to be involved in the acute stimulation of steroidogenesis. The 57,000 Da protein is the regulatory subunit of the cAMP-dependent protein kinase. The 22,000, 24,000 and 33,000 phosphoproteins are present in microsomes and may regulate the synthesis of specific rapidly-turning-over protein(s) which in turn may stimulate the mitochondrial cholesterol side-chain cleavage activity.

Animals↗
PubMed1982

Lutropin increases phosphorylation of a 33 000-dalton ribosomal protein in rat tumour Leydig cells.

Addition of lutropin (luteinizing hormone, 'LH') and 3-isobutyl-1-methylxanthine to tumour Leydig cells stimulated phosphorylation of five proteins, of 17 000, 22 000, 24 000, 33 000 and 57 000 Da. Phosphorylation of these proteins coincided with increased pregnenolone production. Phosphorylation of a 33 000-Da protein was lutropin-dependent in Leydig cells isolated from a Leydig-cell tumour, from immature testes or from mature testes. In tumour Leydig cells this protein was present in the small ribosomal subunit. Incubation of tumour Leydig cells with either cycloheximide or puromycin inhibited both basal and lutropin-dependent pregnenolone production, by approx. 90% and 98% respectively. In contrast, basal pregnenolone production in Leydig cells from immature and mature testes was insensitive to cycloheximide or puromycin. Cycloheximide or puromycin increased phosphorylation of the 33 000-Da phosphoprotein by approx. 130% and 80% respectively (effect of lutropin/3-isobutyl-1-methylxanthine on phosphorylation: 100%). The molecular mass, the subcellular localization and the sensitivity to phosphorylation in the presence of inhibitors of protein synthesis indicate that the 33 000-Da protein could be similar to ribosomal protein S6.

Animals↗
PubMed1982

The secretion, measurement, and function of a testicular LHRH-like factor.

In this paper we have demonstrated the presence and secretion within the testis of a factor that is immunologically distinct from LHRH, but that has receptor-binding and bioactive features similar to LHRH. The major source of this LHRH-like factor is probably the Sertoli cell and, as its site of action appears to be restricted to the Leydig cells, it is possible that it is one of the means by which the Sertoli cell has been postulated to regulate the Leydig cell. All of the available evidence suggests that the action of the LHRH-like factor on the Leydig cell is inhibitory, and it may mediate some or all of the negative effects on the Leydig cell of LH and hCG. The precise role of the LHRH-like factor, particularly under physiological conditions (i.e., low level stimulation with LH), remains to be determined, but the availability of methods for its extraction, measurement, and inactivation should enable this problem to be resolved within the near future. Moreover, the recognition that Leydig cell function may be regulated by local factors within the testis should open up new avenues of research that may lead to improved methods for the regulation of fertility in the male.

Aging↗
PubMed1982

Development and cellular localization of rat testicular aromatase activity.

Oestradiol secretion by isolated Leydig cells, Sertoli cells, myoid cells, germinal cells and liver cells from rats of different ages was measured by a validated radioimmunoassay technique. All cells, except germinal cells and liver cells, produced oestradiol when incubated in the presence of testosterone. Sertoli cells from 7- and 10-day-old rats and from prenatally irradiated adult rats were 7 times more active than cell preparations from 15--50-day-old rats. The oestradiol production in Sertoli cells prepared from 7--25-day-old rats could be stimulated with FSH. Oestradiol production by isolated Leydig cells from mature animals was 3--4 times greater than that with preparations from immature animals. LH had no effect on oestradiol production, but testosterone production was stimulated more than 5-fold. The oestradiol production by the isolated cells was affected by culture time, the presence of fetal calf serum in the culture medium and incubation temperature. During a culture period of 6 days oestradiol production by immature Sertoli cells increased more than 5-fold and that by Leydig cells decreased to about 10%. Oestradiol levels in testes from 10--50-day-old rats were approximately 20% of those in testes from 7-day-old animals.

Age Factors↗
PubMed1982

The effects of short-term culture and perifusion on LH-dependent steroidogenesis in isolated rat Leydig cells.

Tumour Leydig cells and normal mature Leydig cells lost their steroidogenic response (pregnenolone and testosterone secretion) to LH after 24 h of culture. Immature cells showed a 2-fold increase in the basal pregnenolone secretion and no change in the LH-dependent pregnenolone secretion after 24 h of culture, whereas the LH-dependent steroidogenesis decreased after 48 h. None of the 3 cell preparations showed morphological signs of degeneration during a culture period of more than 7 days. Histochemical 3 beta-hydroxysteroid dehydrogenase activity in isolated immature Leydig cells disappeared during the first 2 days of the culture period and re-appeared after 5--7 days. Testosterone production by mature Leydig cells decreased during the first hours after exposure to LH, whereas pregnenolone secretion remained constant. From these results it was concluded that Leydig cells attached to plastic can be used for investigation of acute actions of LH on steroidogenesis. A perifusion technique for cells attached to plastic was developed and was applied to the kinetics of LH action on steroidogenesis in tumour and immature Leydig cells. The first stimulation of pregnenolone secretion occurred within 5 min, but a full stimulation was only obtained after 20--30 min. This was followed by a gradual decrease in the stimulated steroid secretion to approximately 50% after 60 min.

Animals↗
PubMed1982

Regulation of survival of rat pachytene spermatocytes by lactate supply from Sertoli cells.

During incubation of fragments of seminiferous tubules in the absence of glucose, pachytene spermatocytes and round spermatids died within 24 h, while Sertoli cells were still viable. The germ cells survived for at least 72 h in seminiferous tubule fragments which were incubated in the presence of glucose. Lactate rather than glucose is essential for [3H]uridine incorporation and survival of isolated pachytene spermatocytes. However, if the spermatocytes were incubated in the presence of Sertoli cells, glucose maintained the incorporation of [3H]uridine into the germ cells. Sertoli cells secreted lactate in the presence of glucose and the lactate secretion was stimulated 2--4-fold by FSH. It is concluded that the activity and survival of pachytene spermatocytes in vitro can be regulated by the supply of lactate from Sertoli cells.

Animals↗
PubMed1981

Lutropin-dependent protein phosphorylation and steroidogenesis in rat tumour Leydig cells.

Tumour Leydig cells have been incubated in the presence or absence of lutropin (luteinizing hormone, ;LH'). Stimulation of cells with lutropin (1000ng/ml) in the presence of 1-methyl-3-isobutylxanthine (0.25mm) resulted in increased steroid production and increased protein phosphorylation. When pregnenolone metabolism was inhibited, basal pregnenolone production was 26.9+/-7.4ng/60min per 10(6) cells; stimulated production was 156.1+/-39.5ng/60min per 10(6) cells (means+/-s.d., n=4). Lutropin-dependent phosphorylated proteins of molecular mass 17000, 22000, 24000, 33000 and 57000Da were detected. A significant increase of [(32)P]P(i) incorporation into these phosphorylated proteins was observed concomitant with the increased pregnenolone production. The occurrence of the phosphoproteins in nuclei, mitochondria and postmitochondrial-supernatant was investigated. The 17000Da phosphoprotein was found in the nuclear fraction, whereas the 22000, 24000, 33000 and 57000Da phosphoproteins were localized in the postmitochondrial-supernatant fraction. Of the cholesterol-side-chain-cleavage activity, 80.3+/-6.1% (mean+/-s.d., n=5) was present in the mitochondrial fraction isolated from tumour Leydig cells, and this activity was 2.5-fold increased when cells had been preincubated with lutropin/1-methyl-3-isobutylxanthine (basal production: 194.6+/-28.6ng/30min per mg of protein; lutropinstimulated production: 498.8+/-91.5ng/30min per mg of protein; means+/-s.d., n=3). The similarities in the kinetics of the phosphorylation of proteins and the pregnenolone production after addition of lutropin/1-methyl-3-isobutylxanthine indicate that the phosphoproteins could be involved in the lutropin-dependent increase in steroidogenesis in tumour Leydig cells. It remains to be demonstrated, however, to what extent the phosphoproteins outside the mitochondria can influence the cholesterol-side-chain-cleavage activity inside the mitochondria.

1-Methyl-3-isobutylxanthine↗
PubMed1981

Sertoli-Leydig cell communication via an LHRH-like factor.

The primary function of the testosterone secreted by Leydig cells is the maintenance of spermatogenesis and hence fertility. This action of testosterone is mediated by the Sertoli cells which nourish and support the developing spermatozoa. As normal Sertoli cell function is so critically dependent on normal Leydig cell function, a regulatory influence of the Sertoli cells on the Leydig cells has been suggested. Indeed, follicle-stimulating hormone (FSH), which acts only on Sertoli cells, can also cause profound changes in Leydig cell function, although how this is effected is unknown. We recently hypothesized that the Sertoli cell might be the source of a luteinizing hormone releasing hormone (LHRH)-like factor which we detected in the interstitial fluid surrounding the Leydig cells. As injected LHRH agonists cause impairment of gonadal function and directly inhibit FSH-induced changes in Leydig cell function through specific membrane receptors, this 'LHRH-like' factor has all the correct credentials for the postulated messenger between the Sertoli and Leydig cells. Here, we strengthen this case by demonstrating that seminiferous tubules from both the rat and the stumptailed macaque (Macaca arctoides) contain a factor which has LHRH-like receptor-binding and biological activity in vitro, but which is immunologically distinct from native LHRH. We have also shown that this factor is secreted in vitro by cultured rat Sertoli cells.

Animals↗
PubMed1981

Modulation of steroidogenic activities in testis Leydig cells.

Recent developments in the regulation of testicular Leydig-cell function support the following conclusions. (1) Enzymic activities involved in steroid production in the testis are mainly localized in Leydig cells. The aromatase enzyme complex for oestrogen production appears to be localized in Leydig cells as well as in Sertoli cells. (2) LH- (or hCG-) induced alterations of Leydig cells depend on dose and duration of exposure of the cell to the hormone. Locally produced oestradiol is probably involved in the inhibition of steroidogenesis. (3) The stimulatory action of LH on Leydig cells involves different proteins in concert with the activation of the cleavage activity of mitochondrial cholesterol side-chain. However, most of the functional properties of these proteins are yet unknown. (4) Different populations of Leydig cells are present in the testis. These different cell populations can be characterized by quantitatively and qualitatively different responses to hormones.

Aging↗
PubMed1981

Cellular localization of the Mn2+-dependent adenylyl cyclase (AC) in rat testis.

In the present study we have examined the exact cellular localization of the Mn2+-dependent adenylyl cyclase (AC) in the rat testis. Several pieces of evidence indicate that this testis specific enzyme is exclusively localized to haploid cells in the testis: firstly, the appearance of Mn2+-dependent adenylyl cyclase coincides in time with the occurrence of haploid cells (IC) in the rat testis. Secondly, tests of tfm rats and mice, in which little or no haploid cells are found, exhibit negligible Mn2+-dependent AC activity. Finally, separation of various testicular cells by BSA gradient sedimentation (Staput fractionation), revealed that this enzyme activity follows the location of haploid cells; the highest specific AC activities being found in the fractions containing elongated spermatids. Some activity found in the primary spermatocyte fraction (4C cells) can to a large extent be explained by the contamination of haploid cells in this fraction.

Adenylyl Cyclases↗
PubMed1981

Exogenous lactate is essential for metabolic activities in isolated rat spermatocytes and spermatids.

Spermatocytes and round spermatids were isolated from rat testis and the effects of addition of 3.3 mM-glucose and 6 mM-DL-lactate to the incubation medium on the morphology, oxygen consumption and incorporation of uridine and amino acids of these cells were investigated. Addition of lactate to isolated germ cells increased O2 consumption 1.8-fold and incorporation of precursors of RNA and protein by at least 5-fold. The amino acid incorporation into spermatocytes and spermatids was irreversibly decreased after a preincubation for at least 5 h or 70 min respectively in the absence of lactate, indicating degeneration of the germ cells. In the presence of lactate, however, spermatocytes maintained their morphological integrity for at least 24 h. Addition of glucose to isolated germ cells had no effect on any of the parameters investigated. It is concluded that isolated spermatocytes and round spermatids may utilize lactate, perhaps secreted by Sertoli cells, as the main source of energy.

Animals↗