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

Abstract

Summary. Minces of the testes of bank voles, born and reared in a long (18L:6D) photoperiod until weaning (18\p=n-\22days of age) and subjected thereafter to a short (6L: 18D, Group S) or a long (18L:6D, Group L) photoperiod for 6\p=n-\9weeks, were incubated with [4-14C]17\g=a\-hydroxyprogesterone in the presence of cofactors (NADP/ NADPH, 1\m=.\3 mmol/l) for 1 h at 37\s=deg\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\g=a\-hydroxy,20\g=a\-dihydroxyprogesterone(43\m=.\3%). In Group S there was a decreased production of 1 7 \ g = a \ -h y d r o x y , 2 0 \ g = a \ -d i h y d r o p r o g e s t e r o n e and androgens (25\m=.\4% and 10\m=.\4%respectively) and a substantial portion of the substrate was not metabolized (38\m=.\8%). The main androgen metabolites identified, androst-4\x=req-\ ene-3\g=b\,17\g=b\-diol and 5\g=a\-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\g=a\-hydroxysteroid dehydrogenase.

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

“…The present study indicates that a short photoperiod arrests the induction of LH receptors as well as the increase in Leydig cell numbers associated with normal testicular maturation (Knorr, Vanha-Perttula & Lipsett, 1970;Huhtaniemi & Catt, 1981 (Tähkä et al, 1982(Tähkä et al, , 1983aTeräväinen & Tähkä, 1985). There seems to be a good correlation, especially in the short photoperiod group, with the changes in LH receptor numbers per testis and the other functional indicators investigated in our earlier studies, i.e.…”

“…Of special interest was to compare the temporal changes in LH receptor numbers in stimulatory and inhibitory photoperiods to the results of our earlier studies (Tähkä, Teräväinen & Wallgren, 1982, 1983bTähkä, Ruokonen, Wallgren & Teräväinen, 1983a;Teräväinen & Tähkä, 1985) Histological evaluation ofLeydig cell numbers. The material from our earlier study (Tähkä et al, 1983a) (Greenwood, Hunter & Glover, 1963) as described by Markkanen, Töllikkö, Jääskeläinen & Rajaniemi (1980).…”

Photoperiod-Dependent Effects of 4-tert-Octylphenol on Adherens and Gap Junction Proteins in Bank Vole Seminiferous Tubules

“…In the testes of males kept in short light cycles most of seminiferous tubules exhibit small or no lumen with not fully differentiated germ cells. Decrease in the level of plasma gonadotropins during the short photoperiod results in reduced testosterone production decreased expression and activity of steroidogenic enzymes and reduced expression of androgen receptor when compared to long-day animals [17, 27, 28]. The present study provides clear evidence that in bank voles also direct cell-cell interactions are regulated by length of the light cycle, since the expression and localization of protein markers of adherens and gap junctions are different in animals reared under different light conditions.…”

Current aspects of Leydig cell function and its regulation

“…Desensitization seems to be specific for the mature Leydig cells. However, the steroidogenic response of the Leydig cell to an LH signal is not Stereotypie but dependent on the LH dose as well as the developmental stage of the gonads (Ficher & Steinberger, 1971;Huhtaniemi et al, 1982Huhtaniemi et al, , 1984aTähkä, Teräväinen & Wallgren, 1982, 1983bTähkä, Ruokonen, Wallgren & Teräväinen, 1983a;Teräväinen & Tähkä, 1985;Bartke et al, 1985a;Moyle et al, 1985). It has been proposed that the lack of heterologous and homologous downregulation in the Leydig cells of neonatal and fetal animals is an adaptation to high levels of placental hCG and reflects the need for high androgen concentrations during differentiation of the genitalia and the masculinization of hypothalamic structures in the male fetus (Huhtaniemi et al, 1984b).…”