Relationship between renal prostaglandin E and renal sodium handling during water immersion in normal man.

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Abstract
Previous studies have reported that the central hypervolemia induced by H2O immersion to the neck (NI) constitutes a suitable model for assessing the hormonal response to volume expansion without concomitant alterations in plasma composition. The NI model assessed in a kinetic fashion the relationship between renal prostaglandin E (PGE) and renal Na handling. Normal subjects (9) were studied 2 .times. in the Na-replete state during NI: with indomethacin (Ind) pretreatment (50 mg every 6 h, 5 times) (NI + Ind) and without indomethacin (NI). Urinary Na, K and PGE excretion (UPGEV) were measured hourly. NI was associated with marked increases in UNaV [from 87 .+-. 20 (SE) to 219 .+-. 25 .mu.eq/min (P < 0.05)] and UPGEV[from 6.4 .+-. 1.4 to 12.9 .+-. 2.5 ng/min (P < 0.05)]. Although indomethacin administration lowered the basal rate of UPGEV prior to immersion, it neither prevented the subsequent augmentation of UPGEV during NI + Ind nor affected the magnitude of the natriuresis during NI + Ind. Of the subjects 6 were restudied following dietary Na restriction (10 meq/day). The changes in UPGEV during NI and NI + Ind were qualitatively similar to those observed in the Na-replete state. Natriuresis of immersion was attenuated markedly by indomethacin pretreatment. Immersion-induced central volume expansion was associated with a striking increase in renal PGE excretion which was attenuated but not prevented by indomethacin. Indomethacin administration attenuates markedly the natriuretic response of immersion in Na-depleted, but not in Na-replete, normal subjects. Renal PGE may possibly constitute a determinant of the renal response to volume expansion in Na-depleted man.