Transport of some non-electrolytes through amphibian skins

Amphibian skin diseases

Skin diseases in amphibian species seem to carry an additional degree of seriousness compared with those of other vertebrates. Because of the skin's importance in respiration and ion transport, breaching of the integument of these animals can result in fatal septicemias or metabolic disturbances. The timely diagnosis and treatment of these skin lesions is important. A review of the diseases affecting amphibian skin is provided. This article also describes the clinical signs, appropriate diagnostic steps, and treatment and control of amphibian skin diseases.

Noradrenaline induced secretion of nonelectrolytes through frog skin

Addition of noradrenaline (4 x 10(-5) M) to the inner bathing fluid in the skin of the frog Rana esculenta results in increased unidirectional fluxes of urea, thiourea, N-methyl-thiourea, N-N'-dimethylthiourea and mannitol. Fluxes towards the external medium (phi o) undergo a much greater increase than those moving the opposite direction (phi i). The effect of noradrenaline on phi o is higher for urea and thiourea than mannitol, while its effect on phi o thiourea derivatives is related to lipid solubility. This phenomenon does not occur for phi i of the same molecules. FCCP (10(-6) M) pretreatment strongly inhibits the noradrenaline effect on phi o. In skin pretreated with colchicine (2 x 10(-5) M) both urea fluxes are increased to the same extent by noradrenaline. Noradrenaline is concluded to exert two separate effects: (1) a change in permeability in both directions; (2) a secretion of nonelectrolytes towards the external fluid. Such secretion is most probably associated with the hormone-induced secretion of fluid and electrolytes, perhaps mediated by an exocytotic mechanism.