PLASMA TESTOSTERONE SURGE AND LUTEINIZING-HORMONE-BETA (LH-BETA) FOLLOWING PARTURITION - LACK OF ASSOCIATION IN THE MALE-RAT

Studies examining the role of luteinizing hormone (LII) in the initiat ion of the postnatal surge of testosterone in the male rat have produc ed ambiguous results. We examined the pattern of postnatal LH secretio n in the newborn male rat, coincident with plasma testosterone levels, using a specific monoclonal antibody for LH-beta. In some males, we a ttempted to block LII secretion and the postnatal testosterone surge b y injecting males with a gonadotropin-releasing hormone (GnRH) antagon ist, an LH antibody or progesterone immediately after delivery by cesa rean section on day 22, Following injection, animals were immediately sacrificed (time 0) or housed in a humidified incubator maintained at 30 degrees C until sacrifice at 60, 120, 240, 360 or 480 min after del ivery, Plasma from individual animals was measured subsequently for LH -beta and testosterone by radioimmunoassay. Results revealed a postnat al surge of testosterone which peaked at 2.h after delivery in males f rom all treatment groups. This testosterone surge was not accompanied by a postnatal rise in plasma LH-beta in any group, Administration of the GnRH antagonist or the ethanol vehicle produced a transient drop o f approximately 25% in LH-beta levels at 60 min but did not decrease t he postnatal testosterone surge in the same animals. Additional studie s in untreated males and females born by cesarean section or natural b irth also failed to reveal a postnatal rise in plasma LH-beta during t he first 3 h after birth. Plasma levels in both sexes were significant ly lower in animals delivered by cesarean section compared to natural birth. Overall, these results indicate that the postnatal surge of tes tosterone occurs without a corresponding surge of detectable LH-beta i n the male rat.