Relationship Between Perfusion Pressure and Coronary Vasoreactivity in Saline Perfused Hearts Isolated from Normotensive and Spontaneously Hypertensive Rats: Role of Endothelium

Although reduced endothelium—dependent coronary vasodilation is a consistent finding in patients with hypertension, studies in perfused hearts isolated from spontaneously hypertensive rats (SHR) lead to controversial results. One possible explanation is that coronary vascular reactivity in SHR hearts were studied at different fixed perfusion pressure levels, which were outside the arterial blood pressure range found in these animals. Therefore, the objective of the present experiments was to systematically study the effect of an endothelium-dependent (serotonin) and endothelium—independent (sodium nitroprusside, SNP) vasodilator on coronary flow rate at a wide range of perfusion pressure levels (55 to 130 mmHg) in saline perfused hearts isolated from normotensive (NWR) and SH rats. The pressure-flow relationship showed coronary flow autoregulation at different pressure levels in the two groups (55 to 90 mmHg in NWR hearts and 110 to 130 mmHg in SHR hearts). At a maximally effective concentration (104M) co...