Cold and dehydration induce changes in expression of glyceroporin HC3 in three tissues from gray tree frogs Hyla chrysoscelis

Abstract

Gray tree frogs, Hyla chrysoscelis, are potentially subject to dehydrational challenges from evaporative water loss and from freezing. In anticipation of the latter, this species accumulates glycerol during cold acclimation. We hypothesized that expression of the AQP HC3, a protein from the glyceroporin family that transports both water and glycerol, is up‐ regulated in response to cold and dehydration. We used immunohistochemistry to compare the expression levels of aquaporin HC3 in liver, kidney and skin of control (hydrated, 23º C), cold (hydrated, 4º C) and dehydrated (loss of 20% of standard body mass over one week at 23º C) gray tree frogs. During dehydration, expression of HC3 was markedly increased in liver, kidney and skin compared with control tissues. In contrast, HC3 expression was diminished in kidney and skin from cold animals, but was highly expressed in cold liver compared with warm and dehydrated conditions. The up‐regulation in HC3 protein expression in cold liver may reflect the role of this organ in synthesis and release of glycerol, whereas up‐regulation in kidney and skin during dehydration may reflect a regulated role of the aquaporin in water conservation. Research supported by NSF IOB‐0517301.