Renal contribution to plasma catecholamines--effect of age

In 18 subjects undergoing diagnostic cardiac catheterization renal venous noradrenaline during rest (296 +/- 26 ng/l, mean +/- SE) was significantly increased over arterial noradrenaline concentrations (250 +/- 20 ng/l, P less than 0.01) while, in contrast, the arterial adrenaline level (79 +/- 9 ng/l) was higher than the renal venous (41 +/- 4 ng/l, P less than 0.001). Age correlated positively with both renal venous noradrenaline (r = 0.56) and the renal venous-arterial difference of noradrenaline (r = 0.56), and negatively with arterial (r = -0.52) and renal venous adrenaline (r = -0.48). According to our data, a net renal venous secretion of noradrenaline and at the same time an uptake of adrenaline from the renal circulation take place at an extent that may influence plasma concentrations of both. With increasing age renal uptake of plasma adrenaline seems to decrease and net release of noradrenaline to increase. The fall in plasma adrenaline may be due to age-dependent involution of the adrenal medulla. In studies of plasma adrenaline concentrations and of the renal handling of plasma catecholamines the influence of age must be taken into account.