The sequence of changes in prepubertal male rat serum testosterone following intravenous injection of rat LH.

Mean serum testosterone concentration in the 27-day-old prepubertal Holtzman rat was 0\m=.\25ng/ml, much lower than that observed in the adult male, 5\m=.\5ng/ml. Within 15 min after the intravenous injection of rat LH (in a dose of 400 ng-equiv. NIH-LH-S1/100 g body weight) serum testosterone concentration in the prepubertal rat increased approximately fivefold. Maximal elevation of serum testosterone to levels as high as those observed in the adult male occurred 1 hr after intravenous injection of rat LH. Serum testosterone returned to `control' levels within 2 hr of the intravenous injection of a small dose of rat LH. A dose-response relationship existed between serum testosterone and the dose of rat LH injected intravenously, over the range 25 to 1600 ng-equiv. NIH-LH-SI/100 g body weight.