Effects of catecholamines on electrolyte transport in cortical collecting tubule

We examined the direct effects of isoproterenol (ISO) and L-norepinephrine (NE) on electrolyte transport in isolated rabbit cortical collecting tubules (CCT) perfused in 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 beta-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 for 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 less than 0.005). In conclusion, both ISO and NE and capable of decreasing PD in rabbit CCT perfused in vitro. This effect is mediated by beta-adrenergic receptors and is accompanied by the increase in net chloride absorption. Although the mechanism responsible for this decrease in PD with ISO in unclear, active chloride absorption, active hydrogen secretion, or membrane chloride permeability changes may account for the effects of ISO.