Effect of water deprivation on urinary excretion of PGE2 in the dog.

We examined the influence of the state of hydration on the urinary excretion of prostaglandin E2 (PGE2) and kallikrein in the dog. Immunoreactive PGE2 and kallikrein were measured in the urine of conscious dogs during periods of water deprivation and periods of free access to drinking water and in the urine of time-control dogs that had free access to water throughout the study. During water deprivation the excretion of kallikrein did not change significantly, but PGE2 excretion increased by 50 and 75% (P less than 0.05) after 2 and 4 days, respectively, associated with reductions of body weight and urine flow and with elevation of plasma renin activity, plasma sodium, and both plasma and urine osmolality. Dehydrated dogs drank copiously when allowed free access to water, and over the following 4 days both PGE2 excretion and plasma renin activity fell significantly, associated with elevation of body weight and urine volume and with lowering of plasma sodium and plasma and urine osmolality. In contrast, if after 4 days of water deprivation the dogs were kept at a constant level of dehydration by restricting their water allotment on subsequent days to 300 ml/day, PGE2 excretion and most other variables remained at the dehydration level. In conclusion, these results suggest that renal PGE2 production is dependent on the state of hydration in the dog.