A hyperpolarization-activated, cyclic nucleotide-gated, ( I h -like) cationic current and HCN gene expression in renal inner medullary collecting duct cells
2008; American Physical Society; Volume: 294; Issue: 4 Linguagem: Inglês
10.1152/ajpcell.00616.2006
ISSN1522-1563
AutoresJ. J. Bolívar, Dagoberto Tapia, Gabina Arenas, Mauricio Castañón-Arreola, Haydée Torres de Oliveira, Elvira Galarraga,
Tópico(s)Cardiac electrophysiology and arrhythmias
ResumoThe cation conductancein primary cultures of rat renal inner medullary collecting duct was studied using perforated-patch and conventional whole cell clamp techniques. Hyperpolarizations beyond −60 mV induced a time-dependent inward nonselective cationic current ( I vti ) that resembles the well-known hyperpolarization-activated, cyclic nucleotide-gated I h and I f currents. I vti showed a half-maximal activation around −102 mV with a slope factor of 25 mV. It had a higher conductance (but, at its reversal potential, not a higher permeability) for K + than for Na + ( gK + / gNa + = 1.5), was modulated by cAMP and blocked by external Cd 2+ (but not Cs + or ZD-7288), and potentiated by a high extracellular K + concentration. We explored the expression of the I h channel genes (HCN1 to -4) by RT-PCR. The presence of transcripts corresponding to the HCN1, -2, and -4 genes was observed in both the cultured cells and kidney inner medulla. Western blot analysis with HCN2 antibody showed labeling of ∼90- and ∼120-kDa proteins in samples from inner medulla and cultured cells. Immunocytochemical analysis of cell cultures and inner medulla showed the presence of HCN immunoreactivity partially colocalized with the Na + -K + -ATPase at the basolateral membrane of collecting duct cells. This is the first evidence of an I h -like cationic current and HCN immunoreactivity in either kidney or any other nonexcitable mammalian cells.
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