Interactions between furosemide and vasopressin on hemodynamics and on water excretion by the isolated dog kidney.

The effects of furosemide were studied on isolated dog kidneys in the absence and in the presence of vasopressin. In the latter condition, furosemide did not modify renal blood flow and glomerular filtration rate while both parameters were decreased by the drug in the absence of vasopressin, as they were also reduced by vasopressin alone. This would indicate direct vasoactive effects of furosemide, depending on the previous tone of the vasculature. In the absence of vasopressin, furosemide decreased free water clearance through inhibition of sodium reabsorption in the ascending limb of Henle's loop. On the other hand, in the presence of vasopressin, furosemide increased free water clearance, presumably through reduction of water reabsorption in the collecting duct by enhanced distal tubular flux.