Correlation between hcg (lh)-binding capacity, leydig cell number and secretory activity of rat testis throughout pubescence.

Male rats varying in age from 10 to 110 days were examined for testosterone concentration of serum and testicular tissue and 125-I-HCG-binding capacity of testicular tissue. In addition, the Leydig cell number of testes was determined using two different staining methods. It could be demonstrated that specific 125-I-HCG-binding capacity of rat testis increased with age up to 60 days of life. This rise was accompanied by an increase in serum and testicular testosterone concentrations and can be explained by a concomitant increase in Leydig cell number up to this age. The calculated specific 125-HCG-binding capacity per Leydig cell does not change from day 30 to 110 of life. This finding is in contrast to the 125-I-HCG-binding capacity per Leydig cell at day 10 and 20, the former being 5-6 times higher than in the age groups of 30 to 110 days. The observation of high 125-I-HCG-binding capacity per Leydig cell at day 10 and 20 is discussed in the light of simultaneous elevated serum and testicular testosterone concentrations.