Changes in Leydig cell function during sexual maturation in the mouse

Changes in androgen production by isolated Leydig cells were evaluated from 20 through 60 days of age in the mouse. Leydig cells were obtained by mechanical dissociation of testes, purified by centrifugation in metrizamide gradients, and incubated with increasing concentrations of human chorionic gonadotropin (hCG). Testosterone and 5 alpha-androstane-3 alpha, 17 beta-diol (androstanediol) were measured by radioimmunoassay in samples of cells plus medium. Sensitivity of mouse Leydig cells, evaluated as the concentration of hCG that elicited half-maximum androgen responses, was essentially the same at all ages. Maximum testosterone production increased by about 20-fold from 20 to 45 days of age but was no greater at 60 days than at 45 days. Maximum androstanediol production increased by about 3- to 4-fold from 20 to 25 days and declined after 30 days of age. Androstanediol predominated over testosterone by about 2-fold at 20 days; this relationship was reversed by 30 days, and at later ages testosterone greatly predominated over androstanediol (by at least 4- and 6-fold at 45 and 60 days of age, respectively). Maximum total androgen production, estimated from the sum of the values for testosterone and androstanediol, increased by about 7-fold from 20 to 30 days of age and remained essentially constant thereafter. These results are compared with those from previous studies of the rat.