Myocardial expression of hyperpolarization-activated, cyclic nucleotide-gated proteins in healthy cats and cats with hypertrophic cardiomyopathy

In this article the myocardial expression of different hyperpolarization-activated, cyclic nucleotide-gated (HCN) isoforms in myocardial tissue from healthy control cats and cats with hypertrophic cardiomyopathy (HCM) was evaluated. Myocardial tissue samples of the left ventricle of control cats (n = 12) and cats with HCM (n = 4) were collected. Expression of feline HCN was determined by immunoblot analysis using antibodies against HCN2 and HCN4. Optical densities of HCN bands were compared among groups by use of the Mann-Whitney Rank Sum test. HCN4 was reliably detected in myocardial tissue whereas HCN2 was not. HCN4 expression was significantly increased in left ventricular (LV) myocardial samples of cats with HCM (P = 0.036) compared to control cats. Results indicate that myocardial HCN4 expression can be evaluated in cats by immunoblot analysis and that HCN4 expression is upregulated in LV myocardial tissue of cats with HCM. The pathophysiological importance of HCN overexpression with regard to myocyte function and altered automaticity deserves further study.