Catecholamine release and blood pressure changes induced by exercise in dogfish.

Plasma norepinephrine (NE), epinephrine (E), and potassium (K+) were measured before, during a 3-min bout of exercise, and at intervals after exercise in Squalus acanthias. The dorsal aortic pressure response following 1 min of exercise was observed in another series of experiments. Plasma E, NE, and K+ increased significantly and progressively during the exercise period and for 2 min after exercise. Plasma E increased significantly during the 1st min; NE during the 2nd min; but K+ did not increase significantly until the 3rd min of exercise. Blood pressure decreased significantly during 1 min of exercise but increased over control level within 4 min after the end of exercise coincident with the peak of plasma E and NE concentrations. Plasma NE, E, and blood pressure decreased slowly in parallel fashion during the 37-min postexercise period of observation. Increased plasma K+ from skeletal muscle is probably not the primary stimulus for early catecholamine release in exercising dogfish, but increased plasma K+ does contribute to releasing and maintaining plasma NE and E levels in the postexercise period. This results in a sustained pressor effect that promotes blood flow and aids in metabolic recovery.