Developmental changes in in vitro testosterone production by dispersed Leydig cells during fetal life in rats

The age-related evolution during fetal days 18.5-21.5 of the capacity of collagenase-dispersed Leydig cells to produce testosterone and to respond to LH or dibutyryl cyclic AMP (dcAMP) was studied in vitro in the rat. When dispersed Leydig cells were incubated in control medium, testosterone secretion by cells from 18.5-day-old fetuses during the first 5 h was 100 and 50% higher than secretion by cells from 20.5- and 21.5-day-old fetuses, respectively. The secretion maximally stimulated by 100 ng/mL LH or stimulated by 1 mM dcAMP was also stronger on day 18.5 than on days 20.5 and 21.5 during the first 3 h of culture. The dose-response curves for LH showed that the ED50 was similar for day 18.5 and 20.5 cells (2 ng/mL LH). During the course of 24-h incubation, the secretion rates also changed with time and fetal age: Between 5 and 24 h of culture basal secretion decreased in day 18.5 cells, rose slightly in day 20.5 cells, and increased sharply in day 21.5 cells; in the same way, in the presence of LH or dcAMP, the secretion by day 18.5 cells decreased faster than that of day 20.5 or 21.5 cells. The basal testosterone secretion of the Leydig cells and its maximum steroidogenic capacity decrease during late fetal life in the rat, and there was no change in the sensitivity to LH during this period. The age-related differences in the variations of the secretion rates as a function of the duration of incubation suggest the existence of an evolution in extragonadotropic regulations during late fetal life.