SERUM TESTOSTERONE AND LUTEINIZING HORMONE CONCENTRATIONS IN CASTRATED IMMATURE RATS TREATED WITH TESTOSTERONE

Abstract Department of Physiology and Biophysics, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, B3H 4H7, Canada (Received 28 April 1975) Testosterone has been accepted as the testicular hormone primarily responsible for the feedback regulation of luteinizing hormone (LH) secretion. However, there is some question whether testosterone is the principal androgen produced by the testes of immature rats between 20 and 40 days of age. This is based on considerable evidence that the testes of these animals rapidly convert testosterone and precursors of testosterone to androsterone and 5α-androstane-3α,17β-diol (Coffey, French & Nayfeh, 1971, Steinberger & Ficher, 1971; Moger & Armstrong, 1974a). In addition, 5α-androstan-3α,17β-diol has recently been shown to be a potent inhibitor of serum LH concentrations in immature male rats (Eldridge & Mahesh, 1974). The present study was performed to determine whether the serum testosterone concentrations normally found in 30-day-old male rats are capable of suppressing the castration-induced rise in serum LH