The effects of nifedipine on regional vascular resistance and blood flow in the spontaneously hypertensive rat.

The purpose of the study was to compare the peripheral vascular effects of the calcium blocker nifedipine (NF) in normotensive Wistar Kyoto (WKY; n = 25) rats and spontaneously hypertensive rats (SHR; n = 28). Male eighteen week old animals were anesthetized with pentobarbital (50 mg/kg i.p.) and subjected to the radioactive microsphere technique for measurement of systemic and regional hemodynamics. While NF (30 micrograms/kg i.v. or 100 micrograms/kg i.v.) was effective in reducing resistance in all sampled vascular beds of SHR and WKY, it reduced renal vascular resistance to a greater extent in the SHR than in WKY (p less than 0.025). The data suggested a similar strain-specific effect in the SHR coronary, stomach and brain vasculatures (0.12 less than p less than 0.16). By contrast, high dose NF had a preferential effect on the skeletal muscle vasculature of WKY (p less than 0.025 for blood flow, p less than 0.16 for resistance). The findings support the premise that each calcium blocker has unique regional effects that differ between SHR and WKY.