Effect of hypertension and sodium chloride on vascular reactivity in vitro ∗

Abstract

Rats were rendered hypertensive either by the administration of DCA and salt or by renal constriction. Isometric tensions developed in strips of aorta from these rats, when exposed to epinephrine or levarterenol, were compared with the tensions in aortic strips from normotensive control rats The strips from the hypertensive animals responded, in general, with smaller contractile tensions than did those from the normotensive rats. Contractions of aortic strips from DCA-salt hypertensive rats were also compared with those of strips from control animals in the presence of solutions of altered sodium ion concentration and/or tonicity. The strips from hypertensive animals, in contrast to those from control animals, manifested a slow, prolonged increase in tension in the presence of solutions of elevated sodium ion concentration or tonicity, alone. Addition of epinephrine then caused relatively weak contractile responses in the strips from hypertensive rats while the strips from the normotensive rats contracted even more vigorously than when in normal solutions. These results are interpreted to mean that as a consequence of hypertension, arterial walls became not only structurally but also functionally altered, and that the functional alteration includes a decreased reactivity to catecholamines and a changed contractile behavior in the presence of elevated sodium ion concentrations and/or hypertonic solutions.