Effects of nifedipine and TMB-8 on renal vasoconstriction induced by hypertonic saline in dogs

Intrarenal arterial infusion of hypertonic saline (+30 mEq/l NaCl in renal plasma) reduced renal blood flow and glomerular filtration rate with little change in filtration fraction in anesthetized dogs. The blood flow and the filtration rate responses were suppressed during infusion of nifedipine (0.1 microgram/kg per min). TMB-8 (50 micrograms/kg per min) also suppressed the blood flow response but not the filtration rate response. These results suggest that preglomerular vasoconstriction during hypertonic saline infusion requires Ca2+ influx via voltage-dependent Ca2+ channels and that hypertonic saline slightly contracts postglomerular vessels by activating a TMB-8-sensitive Ca2+ movement pathway.