The effect of prostaglandin E2 and ADH on diffusional water permeability in the collecting duct of an isolated rat papilla

The effect of prostaglandin on diffusional water permeability has been studied in collecting ducts in an isolated rat papilla. PGE₂ increased water permeability. The effect was significant at a concentration of 10^–8 mol l^–1 and was maximal with a concentration of 10^–6 mol l^–1. The maximal increment of 0.94±0.10 (SEM) m s^–1 was approximately half that produced by maximal stimulation with antidiuretic hormone (2.18±0.12 m s^–1).A concentration of 10^–8 mol l^–1 produced an increase in basal water permeability and 25 unit ml^–1 ADH, which without PGE₂ present gave a similar increase, had no incremental effect. ADH 100 unit ml^–1 increased permeability to a value similar to that observed in the absence of PGE₂. Thus PGE₂ and ADH both increase water permeability but the increments are not additive.Indomethacin in a concentration that inhibited prostaglandin production altered the response of the collecting duct to ADH. The dose response curve was shifted to the left and the maximal increase in water permeability and the lowest dose at which a response occurred took place at concentrations less than 1/2 those required in its absence.Prostaglandins influence the action of ADH and it is likely that in life they regulate and modulate the change in water permeability induced by anti-diuretic hormone.