Relative capillary blood flow and Leydig cell function in old rats.

Abstract

The incretory testicular function was investigated in young adult (3 months old) and old (24–27 months old) male Wistar rats. Plasma testosterone ranged from 72–1162 ng/100 ml in the young rats (average, 300 ng/100 ml; n = 35) and from 23–263 ng/100 ml (average, 120 ng/100 ml; n = 31) in the old animals. A significant reduction in plasma LH levels, which were, on the average, 54.4 ng/ml (range, 26.0–95.0) in the young rats and 36.9 ng/ml (range, 5.0–97.5) in the old animals, probably causes the decrease in testosterone secretion observed. To investigate further the consequences of reduced LH secretion in old rats, we have studied the relative testicular capillary blood flow by means of the inert gas clearance technique. A significantly reduced capillary blood flow was observed in the old rats (12.6–55.8; average 32.5 ml/100 g tissue-min; n = 17) when compared with the young rats (28.9–69.4; average, 50.5 ml/100 g tissue min; n = 18). The age-dependent fall in testicular blood flow was completely reversibl...