Defective Renal Handling of Water in the Rat with a Portacaval Shunt

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Abstract
Male rats with a portacaval anastomosis, placed in metabolic cages excreted twice as much urine as unoperated control rats. After s.c. injection of 1 unit of pitressin tannate in oil, the rats exhibited a 27% reduction in fluid intake and a 37% reduction in urine volume. The rats still excreted 60% more urine than control rats. Fluid restriction resulted in a reduction in urine volume and an increase in urine osmolality in both groups of rats. Shunted rats continued to excrete 49 ml kg-1 24 h-1, while drinking only 43 ml kg-1 24 h-1. Owing to the negative water balance, plasma osmolality rose by 22 mosmol/kg H2O. Two wk after portacaval anastomosis arterial prostaglandin-E concentrations were 412 ng/l, compared to 158 ng/l in control rats. Shunt induced diuresis may be due to the renal effects of prostaglandin-E.