Effects of vasopressin on the isolated perfused human collecting tubule

Cortical collecting tubules (CCT) were dissected from the surviving normal tissue of human kidneys removed at operation for either carcinoma or calculus. These CCT's were perfused in vitro shortly after the nephrectomy was performed. Transtubular potential differences in different tubules varied from +3.2 to -2.0 mV and were reduced towards zero by lowering the temperature or by adding ouabain to the bath. In the absence of vasopressin, tubules were essentially impermeable to water with extremely low net water fluxes even in the presence of a transtubular osmotic gradient. Addition of vasopressin to the bath caused the transtubular osmotic water permeability coefficient to increase to values of 125, 175, and 155 X 10(-4) cm/sec in three tubules thus studied. These results demonstrate close similarities between the human CCT and the more extensively studied rabbit CCT.