Adenosine receptor-dependent modulation of inhibin secretion in cultured immature rat Sertoli cells

Inhibitory (A1) adenosine receptors that attenuate adenylate cyclase activity are present in cultured Sertoli cells. To investigate the possible effect of activating these receptors on the secretion of inhibin by the Sertoli cell, immature rat Sertoli cells were incubated for 24 h with follicle-stimulating hormone (FSH) in the absence or presence of the non-metabolizable, adenosine agonist phenyl-isopropyl-adenosine (PIA), and the accumulation of alpha-inhibin immunoreactivity was measured in the medium. Although devoid of effects when added alone, PIA inhibited the FSH-dependent secretion of alpha-inhibin in a concentration-dependent manner (ED50 = 1-1.5 nM). PIA treatment of the Sertoli cells also rendered the cells less sensitive to FSH in terms of alpha-inhibin secretion. The concentration-response curve to FSH was shifted to the right when cells were incubated in the presence of 100-1000 nM PIA. In contrast, dibutyryl cAMP stimulation of alpha-inhibin accumulation was unaffected by treatment with PIA, indicating that the site of PIA action is at the level of cAMP synthesis. These data provide experimental evidence of adenosine modulation of inhibin secretion by the Sertoli cell and suggest that adenosine may act as a local modulator within the pituitary-testicular axis.