Aquaporins, evaporative water loss and thermoregulation in heat-acclimated Mongolian gerbils (Meriones unguiculatus)

Evaporative water loss is an essential strategy to maintain stable body temperature in heat-exposed rodents. However, the thermoregulatory role and adjustment of evaporative heat loss capacity is unclear during prolonged heat exposure. Here, we studied the role of evaporative water loss in thermoregulation in Mongolian gerbils during heat acclimation. After 3 weeks of heat acclimation, gerbils exhibited a lower body temperature than the controls, and no difference in evaporative losses of water from the lung or saliva spreading compared with the controls. Heat acclimation did not alter the expression of aquaporin-1 and aquaporin-5 in the lungs and the expression of aquaporin-5 in the salivary glands. The expression of aquaporin-2 in the kidneys was kept stable, while the expression of aquaporin-1 in the kidneys was down-regulated. In addition, resting metabolic rate and non-shivering thermogenesis of heat-acclimated gerbils were reduced to 51% and 55% of the control group, respectively. Taken together, heat-acclimated Mongolian gerbils can reduce the metabolic thermogenesis without enhancing the evaporative water loss capacity for thermoregulation.