Expression of photoreceptor cyclic nucleotide‐gated cation channel α subunit (CNGCα) in the liver and skeletal muscle

Glucagon and β-adrenergic agents increase cAMP levels and stimulate Ca2+ influx in liver cells. There is no consensus as to the mechanism by which these hormones stimulate the influx of Ca2+. Using mouse retinal rod CNGCα cDNA probes, we cloned rat liver and skeletal muscle, and human hepatic CNGCα subunit sequences showing 97–100% identity with the human rod channel. In order to assess channel activity, the effect of cyclic nucleotides on free intracellular Ca2+ levels of isolated hepatocytes was measured. Dibutyryl-cAMP was more effective in increasing free Ca2+ levels than dibutyryl-cGMP. These data indicate that the CNGCα subunit is expressed in the both liver and skeletal muscle possibly mediating hormonal effects on ion fluxes.