Activity of LH receptor, LH-stimulated cyclic AMP and testosterone production in the Leydig cell of heat-acclimatized rats

Abstract

ABSTRACT Key reactions associated with the capacity of the isolated Leydig cell to synthesize testosterone were studied in male rats acclimatized to a hot environment (33–35 °C, 25–40% relative humidity) and controls (20–22 °C, 30–50% relative humidity). The results demonstrate that acclimatization to heat coincides with: (1) a lower number of human chorionic gonadotrophin (hCG) receptors (P<0·01) in the Leydig cell, (2) higher affinity of the Leydig cell for hCG (P < 0·05), (3) lower hCG-stimulated cyclic AMP production (P<0·05) by the Leydig cell and (4) lower capacity of the Leydig cell to synthesize testosterone (P<0·01) after hCG challenge. It is suggested that the major cellular alteration responsible for the decreased testosterone secretion by the Leydig cell lies distal to the step involving the binding of the trophic hormone to its receptor and that heat-acclimatization induces changes in the integrity of the various cellular membranes leading to the impeded function of adenylate cyclase and 17β-hydroxysteroid oxidoreductase. J. Endocr. (1984) 102, 167–173