Testosterone Can Initiate Spermatogenesis in an Immature Nonhuman Primate, Macaca fascicularis*

Abstract

Four 1-yr-old, i.e., immature, monkeys (M. fascicularis), were treated with testosterone. For the 1st 21 wk, they received testosterone capsules s.c.; thereafter for the remainder of 1 yr, they received weekly injections of 125 mg testosterone enanthate. Four similarly aged monkeys served as untreated controls. The testosteone enanthate injections produced a peak level of 345 .+-. 70 nmol/l (mean .+-. SD) after 24 h and the levels were 187 .+-. 39 nmol/l 7 days later. The overall mean level of circulating testosterone in the untreated monkeys was 3.5 .+-. 1.1 nmol/l. Testicular volumes of the treated monkeys became 6 times larger than those of the untreated monkeys. The testicular testosterone concentrations of the treated monkeys were about 2-4-fold greater than those of untreated immature monkeys but no more than 82% of the normal adult range. Spermatogenesis in varying degrees of completeness was found in the testes of all 4 treated monkeys. Moreover, sperm, including some motile cells were found in ejaculates of 2 monkeys. Apparently, spermatogenesis can be initiated, although not quantitatively, in an immature nonhuman primate by testosterone treatment.