Systemic and Regional Hemodynamics in Normotensive and Spontaneously Hypertensive Rats after Slow-Channel Calcium Blocker Nitrendipine

To determine the effects of the recently synthesized slow channel calcium blocker nitrendipine on systemic and regional hemodynamics, mean arterial pressure, heart rate, cardiac index and organ blood flow distribution were measured with the combined radioactive reference sample and microsphere techniques before and one hour after its oral administration (1 mg or 10 mg/kg). Twenty-week-old normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) conscious male rats were studied. At the 10 mg dose, nitrendipine exerted a hypotensive effect within 15 minutes, and this effect persisted throughout the study. After one hour, mean arterial pressure fell by 14 percent of pretreatment levels in WKY controls; it fell by 25 percent in SHR (p < 0.001). This action was mediated by a fall in total peripheral resistance index (p < 0.01) that was nonuniformly distributed to the organ circulations since blood flow was maintained or increased to brain, heart, kidneys, lungs, and adrenals, but decreased to skin. No change in cardiac index was observed.