ADH-PGE2 interactions in cortical collecting tubule. I. Depression of sodium transport

Antidiuretic hormone (ADH) (200 microunits/ml Pitressin or synthetic arginine vasopressin) causes a transitory increase followed by a sustained decrease in the potential difference (PD) and in the net fluxes of sodium and chloride across rabbit cortical collecting tubules perfused in vitro. The inhibitory action of vasopressin is reversible; removal of the hormone from the bath promotes recovery in the PD and in the transport of sodium and chloride to the level of the controls. After 70 min of incubation with ADH, 10(-5) M meclofenamate, an inhibitor of the synthesis of prostaglandins, was added to the bath of some tubules. Despite the presence of ADH, the PD and ionic fluxes increased to control levels. The introduction of exogenous prostaglandin E2 (10(-5) M PGE2) to the bathing medium containing ADH and meclofenamate mimicked the inhibitory action of ADH, decreasing the PD and the reabsorption of sodium and chloride. Pretreatment of collecting tubules with meclofenamate prevented the inhibitory effect of ADH. These findings show that vasopressin exerts a prolonged inhibitory action on PD and on net reabsorption of Na and Cl and that this action may be exerted through stimulating the biosynthesis of prostaglandin E2 by the cortical collecting tubule.