TESTICULAR GERM-CELL POPULATIONS IN THE ADULT-RAT AFTER CONTINUOUS IN-VIVO TESTICULAR INFUSION OF INHIBIN-A AND ACTIVIN-A

This study investigated the in-vivo effects of inhibin-A and activin-A on germ cell subpopulations in the adult rat testis. Each animal rece ived a total of 2 mu g (dose 5 ng/0.5 mu l/h) of activin, inhibin or 0 .1% bovine serum albumin (vehicle control) delivered intratesticularly into the left testis via a cannula connected to an abdominal minipump implant. To establish whether the hormones exerted any effect on proc arbazine-induced germ cell depletion, a single intraperitoneal dose of this agent was given to a group of the rats 24 h after the start of t esticular infusion of activin or inhibin. Rats were killed 14 days lat er. Inhibin treatment caused a reduction in the number of round sperma tids without altering serum FSH levels. In procarbazine-treated rats, infusion of inhibin reduced the number of pachytene spermatocytes and reduced blood FSH levels simultaneously. Infusion of activin had no si gnificant effect on the numbers of germ cells, but reduced the number of dead cells in the seminiferous tubules of procarbazine-treated rats . The data would therefore suggest that the effects of inhibin and act ivin on the seminiferous epithelium are influenced by the testicular m icroenvironment, and that they are capable of influencing the growth a nd survival of germ cells by both FSH- and non FSH-mediated mechanisms . Further experiments are needed to identify the physiological role(s) of inhibin and activin in spermatogenesis.