CARDIOVASCULAR-RESPONSES TO METABOLIC AND RESPIRATORY-ACIDOSIS AND ANESTHESIA IN LARVAL AMBYSTOMA-TIGRINUM

Larval Ambystoma tigrinum were examined to determine their cardiovascular responses to three types of acidosis: metabolic acidosis via NH4Cl gavage; respiratory acidosis via hypercapnia; and anesthetic-induced acidosis, via triacine methanesulphonate. In addition, another group of(metabolic acidosis) animals were tested to determine the role of beta-mediated catecholamine control on cardiovascular and acid-base regulation. The metabolic and respiratory acidoses produced typical amphibian responses. Anesthesia produced a significant mixed acidosis with respiratory and metabolic components. The cardiovascular responses to metabolic and respiratory acidosis were increased heart rate and pulse pressure. There were no significant changes in diastolic pressure, however, systolic pressure increased as a result of the increased pulse pressure. Animals subjected to metabolic acidosis via beta-blockade with propranolol did not display the increased heart rate and pulse pressure and the acidosis was deepened and prolonged. Anesthesia resulted in a cardiac slowing and increased pulse pressure, probably explained by the Frank-Starling relationship. There was no change in diastolic pressure. Anesthetized animals had depressed blood O-2 tension and elevated blood lactate.