Adaptive Responses to Cold in Arterial Smooth Muscle from Heterothermic Tissues of Marine Mammals

Abstract

PERIPHERAL heterothermy is essential for temperature regulation in many boreal, aquatic or subarctic mammals and birds. Dissipation of heat to the environment is controlled by changes in blood flow to peripheral tissues. Seal flippers are a typical example in which both the skin and deep tissues are normally maintained at temperatures near those of the surrounding water (1°–5° C)¹ but which may serve as heat dissipators when the seal bears a positive heat load. The tissues of a seal flipper are thus able to function normally through a temperature range as large as 35° C while the central or core body temperature is regulated within the narrow range typical of mammals. The present investigation was designed to determine if vascular smooth muscle in several species of seals is functional at temperatures near freezing and whether differences exist between central and peripheral vascular smooth muscle.