Dysfunctional hyperpolarization-activated cyclic nucleotide-gated ion channels in cardiac diseases

Abstract Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are reverse voltage-dependent, and their activation depends on the hyperpolarization of the membrane and may be directly or indirectly regulated by the cyclic adenosine monophosphate (cAMP) or other signal-transduction cascades. The distribution, quantity and activation states of HCN channels differ in tissues throughout the body. Evidence exhibits that HCN channels play critical roles in the generation and conduction of the electrical impulse and the physiopathological process of some cardiac diseases. They may constitute promising drug targets in the treatment of these cardiac diseases. Pharmacological treatment targeting HCN channels is of benefit to these cardiac conditions.

Expression of Voltage-dependent Na+ Channels in the Albino Guinea Pig Cochlea / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: The endolymph produced from cochlear lateral wall regulates fluid and maintains positive endocochlear potential. Although many immunohistochemical studies of ion transport enzymes in the cochlear lateral wall have been reported, their mechanisms are still not completely understood. And there are no reports on the studies of anti-Na+ channels in the cochlea of the guinea pig. The voltage-dependent ion channels are fundamental components of neuronal activity. The Na+ channel has a single alpha subunit with 4 pseudosubunits of 6 transmembrane segments each. Expression of the pore-forming and voltage-sensing alpha or alpha1 subunit typically leads to the appearance of channels with voltage- and time-dependent gating and ion conductance. The purpose of this study is to evaluate the expression of the Na+ channel type I and II in the cochlea lateral wall. MATERIALS AND METHODS: We investigated the protein identification by western blot after homogenization and immunohistochemical localization by FITC to the anti-Na+ channel type I and II in the cochlea of the Preyer's positive, white guinea pigs. RESULTS: The results showed that the anti-Na+ channel type I and II were expressed strongly in the intermediate cells of the stria vascularis, and weakly in the stria vascularis. CONCLUSION: We suggest that there are voltage-dependent Na+ channels in the stria vascularis of cochlea and those functions are further evaulated physiologically by the patch clamp technique.