Temperature-induced phase changes in membranes of heart: A contrast between the thermal response of poikilotherms and homeotherms

Abstract

1. 1. A comparison was made of the differing ability of hearts, isolated from homeothermic and poikilothermic animals, to maintain beating at low temperature. Over the temperature range (0–37°C) differences were observed between the activation energy (or temperature coefficient Q 10 ) for each type of heart. 2. 2. The activation energy for beat rate of the homeothermic heart dramatically increased below approximately 21·0°C. The heart beat of a poikilothermic animal maintained a constant activation energy over the full temperature range 0–37°C. 3. 3. The change in heart beat at 21°C for the homeotherm can be correlated with both temperature-induced phase changes in the lipid components of membranes, and the change in the activation energy of membrane-associated ATPases. None of these changes were observed in the membranes of the heart of the poikilotherm.