CORRELATION OF SEASONAL-CHANGES IN SPERM OUTPUT WITH ENDOCRINOLOGIC CHANGES IN THE ADULT MALE BONNET MONKEY, MACACA-RADIATA

We have examined the monthly variations in sperm output and attempted to correlate the profiles of endocrine hormones secreted with the sper m counts throughout the ,year in the adult male bonnet monkey. As prev iously reported, there was a distinct spurt in sperm output beginning September through December months. A concomitant increase in serum tes tosterone and prolactin concentrations were also noted during Septembe r through November (mid and post-monsoon season). Although there was a marked increase in gonadotropin releasing hormone stimulated testoste rone secretion, the peak testosterone concentrations post gonadotropin releasing hormone injection did not vary significantly (P>0.05) throu ghout the year. Basal serum follicle stimulating hormone concentration s did not vary significantly (P>0.05) during April to June months comp ared to September-November months. Serum inhibin concentration remaine d unaltered throughout the year, except in the month of March. The res ults of this study provide evidence for annual rhythms in prolactin an d testosterone secretion and a distinct seasonality in the sperm outpu t of the adult male bonnet monkey, but the pituitary responsiveness to exogenous gonadotropin releasing hormone remains unaltered throughout the year. Because of the existence of seasonality as noted in the pre sent study, future studies which utilize the adult male bonnet monkey as an experimental model need to take into consideration the seasonal effects on reproductive function in this species.