[Catecholamine receptors and renal function]

Renal function was assessed through clearance studies in man under initial conditions marked by retention (23 experiments) and hydro-saline depletion (19 experiments). Further evaluations were carried out in depletion combined with treatment with (+/-)-propranolol (9 experiments) or with prazosin (9 experiments). In each study, clearance was checked during and after venous infusion of 0.1 micrograms/kg-1/min-1 DA, in addition to the control clearance. Adrenolytic drugs and renal function in hydro-saline depletion. Combination with propranolol had no significant effect on renal function, whereas prazosin led to a significant increase in both total and afferent renal vascular resistance; the flow rate and filtrate were less despite higher arterial pressure. Both the absolute and the percentage loading value of isosmotic and anisosmotic sodium reabsorption were inhibited. Renal action of DA in depletion with and without adrenolytic drugs. DA failed to produce either vasodilatation or a hydro-natriuretic effect during hydro-saline depletion, by contrast with its effect at the same dose during retention. During its infusion, however, it led to sodium saving dependent on stimulation of distal sodium reabsorption; following suspension, this saving increased still further, and there was a significant decrease in flow rate, filtrate and diuresis. Pretreatment with either drug restored the vasodilatatory and hydrosaluretic capacity of DA. Modalities whereby renal function is controlled in the presence of changes in body water and salt content. 1) During retention and during depletion in association with prazosin, anisosmotic transport of sodium is efficient in inverse proportion to the sodium load reaching the diluting segments. Prazosin depresses reabsorption efficiency in the presence of load values similar to those observed during simple depletion. 2) During retention, urinary sodium naturally depends on plasma osmolarity, whereas blood sodium appears to depend on urinary excretion of sodium. During depletion, renal excretion apparently depends on mean blood pressure. These extra-renal control mechanisms probably result in alteration of one or more of the components of the direct line running from the filtrate to the formation urine. 3) When DA is infused during water-salt retention, renal excretory function can be seen to depend on the glomerular filtrate through direct control of diuresis. During depletion in the early stage of DA infusion, on the other hand, the filtrate depends on excretory function through tubulo glomerular feedback control.