Muzolimine modification of renal vasoconstriction.

Utilizing an isolated perfused rat kidney preparation, we studied the modification by muzolimine of changes in glomerular filtration rate (GFR) and renal vascular resistance (RVR). Superimposition of muzolimine upon norepinephrine-induced vasoconstriction revealed that muzolimine returned RVR nearly to control values and increased GFR to supracontrol values. Muzolimine reversed norepinephrine-induced decreases in GFR at concentrations as low as 1 microM, but reduced RVR only at concentrations of 500 microM or greater. Muzolimine also reversed, at least partially, the increased RVR and depressed GFR secondary to potassium-induced depolarization. Although muzolimine has not been shown to possess calcium antagonist activity, our data inicate that it elicits renal actions similar to calcium channel blockers at high concentrations. It also elicits a specific increase in GFR during intense norepinephrine-induced vasoconstriction.