The effect of polyethylene glycol by gavage on electrolyte and water excretion in the rat

The mechanism of polyethylene glycol-induced natriuresis in rats: role of atrial natriuretic hormone

A putative role of atrial natriuretic hormone (ANH) in a polyethylene glycol (PEG) 200-induced natriuresis was examined in conscious Wistar rats. Low molecular weight PEG 200 (0.5 or 1.0 ml/100g body weight) was orally administered to rats by gavage. Urine was collected during a 3 hr test period and blood was obtained at the end of each experiment for measurement of ANH, PRA, clearance studies and for indirect indices of plasma volume. Urinary excretion of sodium and volume increased while plasma ANH concentrations were markedly decreased in a dose-related manner following PEG 200 administration. The osmotic clearance was also elevated following PEG 200 administration. No significant change was observed in any of the parameters following high molecular weight PEG 8000. The observed decrease in ANH was associated with an apparent contraction of plasma volume despite the increased serum osmolality. These data indicate that the ANH inhibitory influence of the decreased plasma volume takes precedence over the stimulatory effect of the hyperosmolality and the latter is primarily responsible for the increased osmotic clearance and natriuresis observed in this model.