Evaporative water loss and tissue dehydration of hamsters in the heat

Abstract

1. 1. Male golden hamsters exposed to 40°C could maintain body temperature below 43.5°C for 2–3 hr and evaporated an average of 10 mg H 2O/g · hr. 2. 2. The evaporation of saliva groomed onto body surfaces accounted for 70 per cent of all evaporation while estimates of respiratory and cutaneous evaporation accounted for 22 and 8 per cent respectively. 3. 3. Desalivation greatly reduced evaporative water loss and heat tolerance. Both the submaxillary-sublingual and parotid glands secreted hypotonic saliva and either set alone produced sufficient saliva to significantly increase evaporative water loss. 4. 4. Water losses were initially supplied by the loss of plasma water. Relative dehydration from vascular, muscular and cutaneous water compartments at the onset of heat exhaustion was less severe in the hamster than in the laboratory rat but hamster muscle and skin contained less water before heat stress than rat tissues. 5. 5. The skin of the hamster contained significantly more fat than the skin of the laboratory rat and kangaroo rat and was better vascularized. The relative thickness of the stratum corneum was significantly thicker and the ventral skin less vascularized in the kangaroo rat than in either the hamster or laboratory rat.