Role of electrolytes in the contractile machinery of vascular smooth muscle

Abstract

The following observations of the effect of imposed alteration in electrolyte composition on the contractility of vascular smooth muscle emphasized the complexity of the processes involved: 1. 1. Studies based on the relation of changes in mechanical performance in response to changes in intracellular potassium (Ki) and in the Ki/Ko ratio constitute strong evidence that the potassium ion can influence vascular smooth muscle response both through its gradient across the cell membrane and by direct action of its intracellular concentration.2. 2. While an increase in potassium concentration in the bath causes only an increase in the magnitude of response of smooth muscle from large conduit vessels, the effect of an increase in potassium concentration on the response of resistance vessels is usually biphasic, small increases depressing and larger increases potentiating the response. These observations constitute further evidence of at least a dual action of potassium.3. 3. Six steroids were compared as to their ability to produce a potentiation of an epinephrine response. The relative potentiating action bore no relation to their known physiologic effects or to their ability to produce hypertension.4. 4. A decrease in sodium concentration in the bath causes an increase in the responsiveness of smooth muscle from both conduit and resistance vessels.5. 5. A decrease in calcium in the bath results in a decrease in the responsiveness of smooth muscle from both of these vessels.