Possible role of endogenous catecholamines in the contractions induced in rabbit aorta by ouabain, sodium depletion and potassium depletion.

Effects of ouabain, Na+ depletion and K+ depletion on the tension development of rabbit aorta were studied. Contraction in the strips was induced by ouabain and Na+-free solution substituted with Li+, tris or sucrose. The contractions were rarely seen under alpha-adrenergic blockade, in reserpinized aorta and mechanically denervated aorta. Contractions induced by norepinephrine were potentiated by Na+ depletion, K+ depletion and ouabain. Contractions induced by high K+ solution were also potentiated by Na+ depletion and ouabain. The potentiation in Li+ solution, K+-free solution and with ouabain was not seen under alpha-adrenergic blockade, in reserpinized aorta and denervated aorta although the potentiation by tris and sucrose solutions was still observed. These data suggest that Na+ depletion, K+ depletion and ouabain release endogenous catecholamines which affect the contraction of the vascular smooth muscle of rabbit aorta.