ACUTE EFFECT OF ETHANOL ON RENAL ELECTROLYTE TRANSPORT IN THE RAT

1. Despite human and animal studies, the direct effect of ethanol on r enal water and electrolyte transport is poorly understood. The acute e ffect of increasing plasma concentrations of ethanol was evaluated in a water diuretic anaesthetized rat model which inhibits endogenous arg inine vasopressin (AVP) release.2. Ethanol at a plasma concentration o f 1.69 +/- 0.28 mmol/L produced an immediate increase in urine now (17 4 +/- 11 mu L/min pre-ethanol and 189 +/- 13 and then 206 +/- 12 mu L/ min during the ethanol infusion; P < 0.01) as well as an increase in f ractional sodium excretion (0.17 +/- 0.04 to 0.28 +/- 0.05 and 0.27 +/ - 0.05%; P < 0.01). There was also a brief phosphaturia. These increas es in electrolyte excretion had returned to control values by 20 min d espite a further increase in the plasma ethanol concentration. 3. The urinary excretion of potassium, calcium and magnesium was not altered nor was glomerular filtration rate or renal plasma flow. 4. Ethanol at a mean concentration of 1.60 mmol/L did not alter the action of a max imal concentration of AVP (75 ng/kg) on water or electrolyte transport . However, the antidiuretic effect of a submaximal concentration of AV P (7.5 ng/kg) was augmented by ethanol at concentrations of 1.63 and 0 .98 mmol/L. 5. These studies suggest that the ethanol induced diuresis commonly ascribed to inhibition of AVP secretion may also be due to o ther intrarenal effects of ethanol, possibly acting within the proxima l tubule. These results also confirm recent in vitro findings that whi le ethanol does not inhibit the action of a maximal concentration of A VP, it does modulate the effects of lower AVP concentrations.