The Journal of clinical investigation
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The importance of plasma protein concentration, renal vascular resistance, and arterial pressure as mediators of the natriuretic response to volume expansion was investigated in anesthetized dogs. Saline loading depressed plasma protein concentration and increased arterial pressure but did not decrease renal vascular resistance. Restoring plasma protein concentration by infusing hyperoncotic albumin increased sodium reabsorption and decreased sodium excretion during saline loading despite simultaneous decreases in renal vascular resistance and increases in arterial pressure. ⋯ However, in kidneys vasodilated before infusing blood sodium excretion increased in response to the infusion in association with increased arterial pressure. This increased excretion of sodium by vasodilated kidneys during infusion of blood could be abolished by reducing perfusion pressure to the preloading level. These observations indicate that changes in plasma oncotic pressure, renal vascular resistance, and arterial pressure either alone or in combination are important variables determining the natriuretic response to volume expansion, and that the relative importance of each of these factors depends on the manner in which volume is expanded (viz., the infusion of saline, plasma, or blood).