Cardiovascular adjustments to enforced activity in the anuran amphibian, Bufo marinus

Abstract

1. 1. Oxygen consumption rate and cardiovascular variables contributing to O 2 transport were measured for marine toads ( S. marinus) at rest and during enforced activity. 2. 2. An 8.3 fold increase in VO 2 with activity was accompanied by elevation of heart rate, systemic arch blood flow, and arterial and venous blood pressures. Systemic arch pulse volume declined slightly with activity. Peripheral vascular resistance declined 40% with activity. Arterial P O 2 and p co 2 increased with activity, whereas pH declined. Venous p co 2 increased and p o 2 and pH declined with activity. Consequently, the arteriovenous difference in p o 2 increased from 12 torr at rest to 62 torr during activity: the calculated arteriovenous difference in blood % saturation increased from 6.5 to 58%. There was a metabolic acidosis during activity. 3. 3. The % contributions of the cardiovascular variables to the VO 2 increment during activity were: heart rate, +17%: systemic arch pulse volume, -2%; arteriovenous % saturation difference, +85%. 4. 4. The large contribution of arteriovenous difference is due to both elevation of arterial and decline of venous saturation.