The adrenergic receptor subtypes present in frog (Rana esculenta) skin

Vito Bellantuono, Giuseppe Cassano, Claudio Lippe, Vito Bellantuono, Giuseppe Cassano, Claudio Lippe, Vito Bellantuono, Giuseppe Cassano, Claudio Lippe

Index: Comp. Biochem. Physiol. C. Toxicol. Pharmacol. 148(2) , 160-4, (2008)

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Abstract

Frog skin transports ions and water under hormonal control. In spite of the fundamental role played by adrenergic stimulation in maintaining the water balance of the organism, the receptor subtype(s) present in the skin have not been identified yet. We measured the increase in short-circuit current ( I SC, an estimate of ion transport) induced by cirazoline, clonidine, xamoterol, formoterol, or BRL 37344, in order to verify the presence of α 1, α 2, β 1, β 2, or β 3 receptor subtypes, respectively. Only after treatment with formoterol, BRL 37344 and, to a lesser extent, cirazoline was measured a significant increase in I SC (57%, 33.2%, and 4.7%, respectively). The formoterol and BRL 37344 concentrations producing half-maximal effect (EC 50) were 1.12 and 70.1 nM, respectively. Moreover, the formoterol effect was inhibited by treatment with ICI 118551 (antagonist of β 2 receptors) while SR 59230A (antagonist of β 3 receptors) had no effect; opposite findings were obtained when the BRL 37344 stimulation was investigated. Finally, by measuring the transepithelial fluxes of 22Na + and 36Cl −, we demonstrated that Na + absorption is increased by activation of β 2 and β 3 and is cAMP-sensitive, whereas the Cl − secretion is only increased by activation of β 2 receptors and is cAMP- and calmodulin-sensitive.