Adrenergic blockade and renal hemodynamics

An isolated blood perfused kidney preparation was used to study the influence of intrarenal adrenergic receptors on renal hemodynamics, renal function, and the renin-angiotensin system. Beta adrenergic blockade with propranolol resulted in a reduction of fractional sodium excretion, and alpha blockade with phentolamine had no effect on sodium excretion despite significant increases in cortical flow and glomerular filtration rate. The changes in sodium excretion after beta blockade were not felt to be due to a direct tubular effect but rather were secondary to preferential perfusion of nephrons in the juxtamedullary cortex, which is known to have higher sodium reabsorptive capacity. These changes appeared to be direct effects of adrenergic blockade on the renal vasculature and were independent of any effects on renin secretion.