Effects of electrolytes on contractility of artery segments in vitro

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Abstract
A 3-cm length of the ventral rat tail artery was excised and mounted in a way that permitted fluid under pressure to flow through its lumen. Muscle activity of the wall was associated with narrowing of the segment and reduction in flow rate at a given intraluminal pressure. The contractility to natural vasopressor agents was studied in normal Krebs solution, in high [K+]0 solutions, and in low [Na+]0 Krebs solutions. Identical responses were produced with 0.1 µg/ml epinephrine, 0.5 µg/ml norepinephrine, 0.4 µg/ml angiotensin II, and 2.5 mU/ml Pitressin, in normal Krebs solution. High [K+]0 Krebs solutions alone constricted the arterial segment and low [Na+]0 Krebs solutions alone distended (relaxed) the arterial segment. High [K+]0 solutions potentiated the response to all four vasopressor agents. In low [Na+]0 sucrose-Krebs, the constrictor response was unaltered for norepinephrine and epinephrine but was reduced for angiotensin II and Pitressin. In low [Na+]0 Li+-Krebs and choline+-Krebs, the constrictor response to norepinephrine was potentiated.