Hormonal and photoperiodic modulation of testicular mRNAs coding for inhibin/activin subunits and follistatin in Clethrionomys glareolus, Schreber.

Photoperiodic and hormonal modulation of mRNAs for testicular inhibin/activin subunits and follistatin were studied in a seasonally breeding rodent, the bank vole (Clethrionomys glareolus). Photoperiod-induced testicular regression had no effect on the relatively low steady-state levels of follistatin mRNA. Inhibin alpha (I alpha) and beta B (I beta B) mRNA levels were significantly higher in regressed than in active gonads, but inhibin beta A was undetectable. The effect of gonadotropin administration on testicular weight and mRNA concentrations differed between the sexually active and quiescent voles. Neither FSH (1.2 U/kg; s.c. for 5 days) nor hCG (600 IU/kg; s.c. for 5 days) affected testicular weight in sexually active voles, whereas both gonadotropins significantly increased testicular weight in photo-regressed individuals. FSH had no effect on I alpha or I beta B mRNA concentrations in the active testes, whereas excessive hCG challenge induced a decrease in the steady-state levels of these mRNAs. FSH induced an increase in I alpha mRNA concentrations in the regressed gonad, whereas both gonadotropins concomitantly down-regulated I beta B mRNA levels. In conclusion, the high expression of I alpha and I beta B mRNA in the regressed testis imply autocrine and paracrine roles for inhibin/activin in the quiescent gonad of seasonal breeders. Inhibin alpha-subunit expression is at least partly under the control of FSH in the bank vole testis.

Photoperiod-induced changes in androgen receptor expression in testes and accessory sex glands of the bank vole, Clethrionomys glareolus.

Photoperiodic modulation of androgen levels and androgen receptor (AR) expression in testes and accessory sex glands were studied in a seasonally breeding rodent, the bank vole. Juvenile voles subjected to long photoperiod (20L:4D) for 6-8 wk attained sexual maturity, which was associated with a prominent increase in testicular testosterone (T) levels and weight of testes and accessory sex glands. Pubertal development in short photoperiod-treated (6L:18D for 6-8 wk) juveniles was arrested, and subsequently reproductive regression set in with a marked decrease in testicular T levels and gonadal weight. In sexually active voles, strong AR immunostaining was detected in nuclei of epithelial, smooth muscle, and stromal cells of the epididymis, prostate, and seminal vesicles. In active testes, AR was present in nuclei of Sertoli cells, peritubular cells, Leydig cells, and vascular smooth muscle cells. In juveniles, strong to moderate nuclear immunoreactivity was encountered in epithelial and stromal cells of the epididymis and prostate, whereas a weaker reaction was discerned in seminal vesicles. In juvenile testes, AR was localized to vascular smooth muscle cells, peritubular, and interstitial cells. In sexually regressed animals, nuclear staining was almost absent in accessory sex glands, whereas in testes, moderate immunostaining was retained in all other cell types except the Sertoli cells. Western blots of active and regressed testes indicated a marked photoperiod-induced down-regulation of immunodetectable AR in the regressed gonad.

Experimental accumulation of lead from soil through earthworms to common shrews.

Common shrews (Sorex araneus) were fed on earthworms containing high concentrations of lead. Both the earthworms and shrews originated from uncontaminated areas, but earthworms for the "lead" group of shrews were reared in the laboratory for 3 or 4 weeks in highly Pb-polluted soil from near an old lead smelter. The control group of shrews received the same amount of earthworms from the uncontaminated area. The acceptance of the experimental food by shrews was significantly lower in the lead group, indicating that the shrews were able to detect the lead in their food. After 2-31 days of feeding, the shrews in the lead group had significantly higher Pb concentrations in their liver, kidney, bone, and pelt than did the controls. Both the number of deaths during the experiment and the proportion of individuals with changes in kidney histology were significantly higher in the lead group.

Hormonal and photoperiod-induced changes in testicular interleukin-1-like factor in bank voles, Clethrionomys glareolus.

Testicular interleukin-1-like factor (tIL-1) is a cytokine secreted presumably by Sertoli cells in several mammalian species. The function of this cytokine is unknown: tIL-1 may control meiosis, act as a mitogen for spermatogonia or have both of these functions. The present investigation was conducted to assess tIL-1 activity and its hormonal control in a seasonally breeding photoperiodic mammal during testicular maturation and photoperiod-induced regression. Testicular maturation in long photoperiod (20 h light:4 h dark) was accompanied by the appearance of tIL-1 activity at the age of 32-39 days which increased as full sexual maturity was reached. No significant tIL-1 activity was detected when pubertal development was inhibited or testicular regression induced by subjecting juvenile and adult bank voles to a short photoperiod (6 h light: 18 h dark) for 6 to 8 weeks. Administration of human chorionic gonadotrophin (hCG; 60 IU kg-1) increased tIL-1 activity in sexually mature as well as regressed testes. In the photoregressed voles FSH (1.2 U kg-1) administration, which induced a three-fold increase in testicular weight and stimulated spermatogenesis, did not induce detectable concentrations of tIL-1. Administration of FSH followed by hCG increased tIL-1 activity significantly in the atrophic testis, but this was probably due to hCG, since FSH treatment alone was without effect. In conclusion, in accordance with the proposed role of tIL-1 as a germ-cell mitogen and a meiosis-promoting factor, tIL-1 activity correlated positively with spermatogenic activity during testicular maturation and photoperiod-induced regression.(ABSTRACT TRUNCATED AT 250 WORDS)

The testes of moles (Talpa europaea) retain a considerable microsomal capacity for androgen synthesis during seasonal regression.

Seasonal changes in testicular histology and steroidogenesis were investigated in the mole (Talpa europaea). Androgen synthesis was examined by incubating [4-14C]pregnenolone (P) and [4-14C]dehydroepiandrosterone (DHA) with testicular minces in a static incubation system. The metabolites formed were characterized by thin-layer chromatography. Morphological changes were studied by routine histological methods. During sexual quiescence spermatogenesis was arrested. The regressive seminiferous tubules consisted predominantly of Sertoli cells and spermatogonia. On the other hand, histological quantification suggested that season has no significant effects on the number or the nuclear dimensions of Leydig cells in this species. The capacity of the regressive testes (per unit weight) to metabolize P and DHA to testosterone (T) was somewhat greater in regressive (48.5%, 49.4%) than in active (33.2%, 41.6%) testes. The results also suggest that the greater in vitro T production encountered during reproductive quiescence is due possibly to an increase in the activity of 17 beta-hydroxysteroid dehydrogenase (per unit weight). Our data on Leydig cell numbers indicate, however, that the capacity of the individual Leydig cells to produce T is decreased during sexual regression. T. europaea appears to be quite exceptional among seasonally breeding small mammals exhibiting pronounced annual changes in spermatogenesis in that the testes retain a considerable enzymatic capacity to produce testosterone from pregnanes during sexual quiescence. The results suggest that pituitary as well as paracrine regulation of the annual testicular cycle in this species differs from that generally encountered in seasonal breeders.

Local control mechanisms in the testis.

The gonads are unique organs in that they harbor the cells of the germline and consequently provide the local environment necessary for the normal development and differentiation of gametes. Since the local requirements for germ differentiation differ considerably from those of somatic cells the structural and physiological organization of the gonad is complex and compartmentalized. An elaborate network of local paracrine interactions between the somatic and gametogenic elements appears to be essential for normal germ cell development in mammals. This is especially true for the testis where meiosis is continuous throughout adulthood and where the spermatogenic cycle of the seminiferous epithelium is strictly controlled in time and space. The present paper reviews briefly the rapidly expanding field of testicular paracrinology. Special emphasis is given to the role of intra- and intercompartmental paracrine communication in the development of the male gamete.

Effect of differential photoperiod treatment on Leydig cell ultrastructure in the bank vole (Clethrionomys glareolus, S.).

Juvenile bank voles (18-22 days of age) born and reared in a stimulatory long photoperiod (18L:6D, lights on 0600-2400 hr) were subjected either to a long photoperiod (18L:6D, Group L) or to a short photoperiod (6L:18D, lights on 0800-1400 hr, Group S) for 6 to 8 weeks whereafter the animals were killed by decapitation. Possible photoperiod-induced changes in Leydig cell ultrastructure were studied by conventional transmission electron microscopy and stereological methods. Striking differences in Leydig cell ultrastructure between the experimental groups were encountered. Light deprivation induced a marked decrease in the cytoplasmic and nuclear volume as well as in the amounts of smooth endoplasmic reticulum (SER), rough endoplasmic reticulum, mitochondria, and lipid inclusions in the Leydig cells. The number of myelin bodies and dense bodies seemed to be somewhat higher in the regressive Group S Leydig cells. These results are in good agreement with our previous histological and biochemical studies on the effects of photoperiod on Leydig cell function and suggest that in the bank vole the volume of mitochondria and SER in particular correlates positively with the steroidogenic capacity (the activity of C20 alpha 22-C27 desmolase, 17 alpha-hydroxylase, and C17-20 lyase in particular) in the Leydig cell.

Current aspects of Leydig cell function and its regulation.

Recent findings on Leydig cell function and its regulation are discussed. Regulatory mechanisms at different organizational levels, i.e. at the level of the pituitary, the testis and the intracellular elements, are briefly reviewed as well as the transmission and the modulation of the hormonal signal at the Leydig cell membrane. Special emphasis is given to local paracrine and autocrine regulatory interactions operating at the level of the testis.

Photoperiodic modulation of testicular LH receptors in the bank vole (Clethrionomys glareolus).

The temporal changes in testicular binding of 125I-labelled hCG in juvenile bank voles (18 days of age, born and reared in a 18L:6D photoperiod) exposed to a long (18L:6D, Group L) or short (6L:18D, Group S) photoperiod for 0, 3, 7, 14 and 42-56 days were investigated. During testicular maturation, in Group L, there was a slight initial decrease in LH receptor numbers per testis followed by a marked prepubertal rise during the initial phase of rapid testicular growth after which a decrease took place. In Group S, during testicular regression, the temporal changes in LH receptor numbers per testis resembled those of Group L except that the corresponding increase in hCG binding during the initial week was considerably less marked and the receptor numbers remained thereafter at a significantly lower level than in Group L. Leydig cell count indicated that the observed changes in LH receptors per testis were due to changes in the number of Leydig cells as well as in LH receptors per Leydig cell. The present results indicate, that (1) photoperiod is an important modulator of testicular LH receptor numbers in this species, (2) photoperiod or age has no significant effect on the binding affinity of LH receptors, (3) short photoperiods arrest the induction of LH receptors as well as the increase in Leydig cell numbers associated with normal testicular maturation, and (4) changes in LH receptor numbers per testis correlate well with the photoperiod-induced changes in androgen biosynthesis, spermatogenesis and Leydig cell morphology observed in our previous studies.

Photoperiod-induced changes in the testicular metabolism of [4-14C]17 alpha-hydroxyprogesterone in the bank vole (Clethrionomys glareolus).

Minces of the testes of bank voles, born and reared in a long (18L:6D) photoperiod until weaning (18-22 days of age) and subjected thereafter to a short (6L:18D, Group S) or a long (18L:6D, Group L) photoperiod for 6-9 weeks, were incubated with [4-14C]17 alpha-hydroxyprogesterone in the presence of cofactors (NADP/NADPH, 1.3 mmol/1) for 1 h at 37 degrees C. The radioactive metabolites were characterized and identified by thin-layer chromatography with derivative formation and chromatography to constant specific activity and isotope ratio. In Group L virtually all of the substrate was utilized and it was readily converted to androgens (48% of the radioactivity recovered) such as androstenedione and testosterone. The only pregnane metabolite identified was 17 alpha-hydroxy,20 alpha-dihydroxyprogesterone (43.3%). In Group S there was a decreased production of 17 alpha-hydroxy,20 alpha-dihydroprogesterone and androgens (25.4% and 10.4% respectively) and a substantial portion of the substrate was not metabolized (38.8%). The main androgen metabolites identified, androst-4-ene-3 beta,17 beta-diol and 5 alpha-androstane-3,17-dione are hormonally quite inert steroids. No androstenedione or testosterone was found. The results indicate that exposure to short photoperiod induces a decrease in the testicular C17-C20 lyase and 20 alpha-hydroxysteroid dehydrogenase.

A histochemical study on the effects of photoperiod on gonadal and adrenal function in the male bank vole (Clethrionomys glareolus).

NADH- and NADPH-diaphorases, 3alpha-, delta5-3beta-, 11beta- and 17beta-hydroxy-steroid dehydrogenases (HSD) and lipids were studied histochemically in the testes and adrenals of male bank voles kept in a long (16L:8D) or a short (8L:16D) photoperiod (Groups L and S, respectively). At 67 days of age the Group L males were heavier and had active and significantly larger testes than Group S males. The testes of Group S males were regressed and were also significantly smaller than those of 18-day-old animals born and reared in a 18L:6D photoperiod. Lipid droplets were detected in the Leydig cells and intratubular spaces in the testes of Group L animals, but were absent from those of Group S voles. The adrenal cortex of the Group L animals was virtually devoid of lipids, but large lipid inclusions were present in the basal zona fasciculata of the Group S voles. In the Group L testes the diaphorase activities were more intense and the difference in enzymic activity between the seminiferous epithelium and the Leydig cells was more pronounced (especially for NADH-diaphorase) than that in the testes of Group S animals. Moreover, the 3alpha-- and delta5-3beta-HSD activities were much stronger in the testes of sexually active animals; 17beta-HSD activity was present in the Leydig cells of the active testes, and absent in the regressed testes. There was no marked difference between the two groups of animals with regard to the distribution or intensity of diaphorases, 3alpha-, delta5-3beta-, 11beta- or 17beta-HSD in the adrenal cortex. It is concluded that a decline in steroid synthesis occurs in the testes of voles kept in a short photoperiod. The large lipid inclusions observed in the adrenal cortex of such animals suggest decreased corticosteroid synthesis and/or secretion.