Effects of catecholamines on electrolyte transport in cortical collecting tubule

Summary We examined the direct effects of isoproterenol (ISO) andl-norepinephrine (NE) on electrolyte transport in isolated rabbit cortical collecting tubules (CCT) perfusedin vitro. The addition of either ISO (10^–6 m) or NE (10^–6 m) to the bath decreased transepithelial potential difference (PD), on average by 51 and 25%, respectively. These effects of ISO and NE were abolished by prior addition of the -adrenergic blocker,l-propranolol. ISO (10^–5 m) had no effect from lumen. Also, osmotic water permeability was not influenced by ISO. Ouabain and ISO had additive effects on PD. Elimination of chloride from both perfusate and bath, or addition of acetazolamide, abolished the effect of ISO on PD. Although isotopic sodium flux from lumen to bath was not influenced by ISO, chemical net chloride absorption increased from 1.1±0.4 to 2.7±0.6 peq·cm^–1·sec^–1 (n=8,p<0.005). In conclusion, both ISO and NE are capable of decreasing PD in rabbit CCT perfusedin vitro. This effect is mediated by -adrenergic receptors and is accompanied by the increase in net chloride absorption. Although the mechanism responsible for this decrease in PD with ISO is unclear, active chloride absorption, active hydrogen secretion, or membrane chloride permeability changes may account for the effects of ISO.