Calcium transport across rat inner medullary collecting duct perfused in vitro

Ca super(2+) transport by the inner medullary collecting duct (IMCD) of normal rats was studied using the "in vitro" microperfusion technique. Ca super(2+) outflux is in part dependent on Na super(+)-K super(+)-adenosinetriphosphatase luminal membrane Na super(+) transport and in part inhibited by verapamil. However, Ca super(2+) influx is independent of Na super(+) transport, is not blocked by verapamil, but is increased by Ca super(2+) transtubular gradient, indicating the presence of a passive diffusion mechanism.