[Extrinsic catecholaminergic control of the renal function during water and salt depletion]

Renal function was studied by means of the clearance method in the healthy subject during hypotonic polyuria induced in initial depletion conditions with or without adrenolytic treatment. Three experiments were performed: a) 19 in water-salt depletion; b) 9 in depletion associated with (+/-)-propranolol; c) 9 in depletion associated with prazosin. 15' clearance periods were carried out during control, dopamine infusion in a subpressor dose (0.1 microgram x kg-1 x min-1) and after suspension, respectively. PAH and endogenous creatinine clearance was also determined, Propranolol made no significant difference to renal function by comparison with simple depletion, whereas the more intense depletive effect of prazosin lead to a significant reduction in renal plasma flow and the glomerular filtration rate. Isosmotic and anisosmotic reabsorption of sodium (in % of the respective loads) was inhibited despite reduction of the filtrate and of the distal sodium load. Dopamine was ineffective as a vasodilator and natriuretic in water and salt depletion, while it displayed significant sodium-retaining properties. Pretreatment with propranolol and prazosin allowed dopamine to show vasodilator and hydrosaluretic effects during depletion. These results are in line with the view that the renal vasal and tubular alpha-adrenergic receptors make a significant contribution to the water and salt conservation associated with volume depletion, and that dopamine influences renal function under these experimental conditions probably by activating prejunctional beta-adrenergic receptors of noradrenergic nerve endings.