Relationship of testosterone pulses to androgen binding in the pituitary of rams

Abstract

The effects of testosterone on cytosol and nuclear androgen receptors of ram pituitary were examined in two experiments. In Exp. I, 500 micrograms testosterone were injected intravenously and groups of 4 rams were slaughtered at 0, 15, 30, 45, 90 and 360 min after injection. Cytosolic receptor concentration decreased from 21 +/- 0.9 to 6 +/- 0.9 fmol/mg protein 30 min after the testosterone injection (P less than 0.001), and then returned towards the preinjection level after 90 min. The pattern of nuclear receptor concentration was the opposite; a maximal increase (12 +/- 3.5 to 32 +/- 5.7 fmol/mg protein) was observed 30 min after injection (P less than 0.001), followed by a progressive but incomplete decrease by 360 min. In Exp. II, blood was collected every 20 min for 17 h in three successive series, each of 12 rams, which were then slaughtered. Plasma LH and testosterone concentrations were measured by radioimmunoassay. No changes were observed in cytosol receptor concentration, but nuclear receptor concentration was negatively correlated with the interval elapsed since the beginning of the last testosterone pulse (r = -0.62; P less than 0.001). The highest values for nuclear receptor concentrations were observed at an interval equal to or less than 120 min. These results indicate that natural pulses are associated with androgen binding particularly in the pituitary nuclei.

Effects of castration on androgen receptors and gonadotropins in the pituitary of adult male viscachas

“…an increase in ARc and a decrease in ARn) in most species studied (Handa and Resko 1988;Kyprianou and Isaacs 1988;Iqbal et al 1995), but exceptions have also been reported (Choate and Resko 1996). After castration, a decrease in the concentration of pituitary ARn was observed (Pelletier et al 1985;Thieulant and Pelletier 1988), indicating a direct relationship between the immunohistochemical detection of ARn and circulating androgens (Iqbal et al 1995).…”