The extent to which the concentrating function of the kidney depends on oxidative processes was investigated by infusing cyanide into one renal artery of dogs undergoing mild mannitol diuresis while receiving an infusion of vasopressin. This produced an abrupt fall in concentrating capacity (TcH2O) that was reversed when the cyanide infusion was stopped. The change could not be accounted for by the accompanying solute diuresis, since it was not reproduced by increasing the rate of mannitol infusion. The reduction in TcH2O induced by cyanide did not result from increased delivery of dilute urine to the collecting ducts, since free water clearance (CH2O), studied in other dogs during water diuresis, was unchanged or decreased by cyanide. Cyanide produced renal vasodilatation, as did intraarterial acetylcholine, but in contrast to the striking reduction in concentrating capacity evoked by cyanide, TcH2O was not significantly changed by acetylcholine.
Edward Weinstein, Andrzej Manitius, Franklin H. Epstein