Secretion of inhibin B by human prepubertal testicular cells in culture.
OBJECTIVE
Inhibin B is a secretory product of Sertoli cells of the human testis. It has been reported that serum levels of inhibin B in infant boys, peaking at 3 months of age, exceed levels in adult men. The aim of this study was to evaluate inhibin B secretion in primary prepubertal mixed testicular cell cultures, prepared from testes collected at necropsy.


METHODS
Cell cultures were divided into three age groups on the basis of differences in testicular histology: group 1 (n = 7), 1- to 10-day-old newborns, group 2 (n = 7), 1- to 9-month-old infants, and group 3 (n = 8), 12- to 84-month-old children. Cells were maintained in culture for 6 days, harvested and counted. In some samples, during the last 4 days, cells were stimulated with 10ng/ml highly purified human (h) LH (n = 9), 2 ng/ml recombinant human (rh) FSH (n = 9) or 50 ng/ml rhGH (n = 4). On day 6, the secretion of inhibin B and testosterone into the medium was estimated in triplicate. Inhibin B was determined by ELISA and testosterone by RIA.


RESULTS
Median (range) inhibin B secretion was 465 (225-1007), 275 (107-298), and 58 (15-184) pg/million cells.24h in groups 1, 2 and 3 respectively. A logarithmic transformation of these values was performed to normalize data. Mean+/-s.d. of transformed inhibin B secretion in group 1 was significantly higher than in group 2 or 3 (P<0.005) and the values for groups 1 and 2 were significantly higher than that for group 3 (P< 0.005). No significant correlation between testosterone and inhibin B secretion into the medium was found when the 22 culture samples were analyzed as a whole. Inhibin B secretion was significantly increased after stimulation with highly purified hLH, rhFSH and rhGH (P < 0.05) and a significant positive correlation between inhibin B and testosterone was found under both hLH and rhFSH stimulation.


CONCLUSIONS
It is concluded that cells collected from newborns have the highest capacity to secrete inhibin B in vitro, and that this capacity decreases with age during the first years of life. Since no data are available on serum inhibin levels in newborns, it is possible that concentrations at 3 months of age do not represent a post-natal peak but a declining level of high newborn values. As expected, FSH stimulated inhibin B secretion in culture. LH stimulation was probably mediated by paracrine factors secreted by interstitial cells. Finally, our results add new evidence of the involvement of GH in testicular maturation.
Berensztein
E
E
Research Laboratory, Garrahan Pediatric Hospital, Buenos Aires, Argentina.
Saraco
N
N
Belgorosky
A
A
Rivarola
M A
MA
D002478:Cells, Cultured; D002648:Child; D004797:Enzyme-Linked Immunosorbent Assay; D005640:Follicle Stimulating Hormone / Q000502:physiology; D019382:Human Growth Hormone / Q000502:physiology; D006801:Humans; D007265:Inhibins / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000502:physiology; D008297:Male; D011627:Puberty; D011863:Radioimmunoassay; D011994:Recombinant Proteins; D013737:Testis / Q000166:cytology / Q000378:metabolism*; D013739:Testosterone / Q000097:blood
D011994:Recombinant Proteins; D019382:Human Growth Hormone; D013739:Testosterone; D007265:Inhibins; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone