Determination of optimum pH for contractility of rainbow trout (Oncorhynchus mykiss) intestine

Aquatic species demonstrate variation in plasma pH in response to stress or disease. Effects of pH on mammalian smooth muscle has yielded species and tissue specific responses. The consequences of altering pH on the contractility of teleost smooth muscle have not previously been examined. Isolated paired segments of rainbow trout (Oncorhynchus mykiss) intestine were suspended at 2 g isometric tension in organ baths containing modified Krebs Henseleit solution at 10 degree C. The pH was adjusted by varying the concentration of CO sub(2) aerating the solution, or with HCl. Results indicate that trout intestinal smooth muscle is sensitive to changes in extracellular pH as occurs during acidosis or alkalosis.