Contractile Responses of Mesenteric Resistance Arteries to BAY K 8644 in Mineralocorticoid-Salt Hypertension

Abstract

Changes in the structure and function of blood vessels are hallmarks of hypertension. Until the recent advent of methods suitable for the study of small resistance arteries, most studies of isolated vascular function in hypertension were conducted on helically-cut strips or rings of large conduit arteries, such as aorta, carotid artery, tail artery, or femoral artery. The extent to which changes in vascular function demonstrated in such systems could be generalized to smaller, resistance arteries has been a matter of debate. The purpose of the experiments presented herein was to compare changes in in vitro vascular contractile sensitivity in conduit and resistance arteries from mineralocorticoid-salt hypertensive and normotensive rats. Contractile responsiveness of carotid arteries and mesenteric resistance arteries to norepinephrine and serotonin was determined. Furthermore, we determined contractile sensitivity to direct depolarization with potassium chloride and to activation of dihydropyridinesensitive voltage-operated calcium channels with BAY K 8644 [methyl-1,4-dihydro-2,6-dimethyl-3-nitro(2-trifluoromethylphenyl)pyridine-5-carboxylate]. We hypothesized that if a generalized change in vascular function is present in mineralocorticoid-salt hypertension, then alterations in contractile sensitivity similar to those seen in conduit arteries would be observed in resistance arteries.