title: The effects of nifedipine on the systemic and coronary vascular beds of the sheep: a potential method for induction of ischaemia.
abstract: Nifedipine has been reported to aggravate symptoms of ischaemic heart disease in some patients. To investigate the possible reasons for this, vascular resistance changes in the systemic and coronary beds of sheep were compared with and without coronary artery stenoses. In six anaesthetized sheep, the dose-response curve comparing vascular resistance to nifedipine dose showed greater sensitivity than that reported for either dogs or humans. The coronary vascular bed was more reactive than the systemic vascular bed but this difference did not reach a level of statistical significance. With fixed non-elastic proximal coronary artery stenoses, the relationship of both coronary flow and coronary resistance to a standard dose of nifedipine (5 micrograms/kg) was indirectly related to the degree of stenosis. With stenosis reducing flow at rest by 50% or more, nifedipine usually produced a reduction in coronary flow in the stenosed artery and associated ST elevation, consistent with severe ischaemia in the distribution of the coronary. This effect is related to the reduction in perfusion pressure.
mesh_terms: D000818:Animals; D003326:Coronary Circulation / Q000187:drug effects*; D003327:Coronary Disease / Q000503:physiopathology*; D005260:Female; D006439:Hemodynamics / Q000187:drug effects*; D008297:Male; D009543:Nifedipine / Q000494:pharmacology*; D012039:Regional Blood Flow / Q000187:drug effects; D012756:Sheep; D014655:Vascular Resistance / Q000187:drug effects
chemical_list: D009543:Nifedipine