Neonatal feline ventricular myocytes exhibited significantly smaller IKs maximum tail current density and faster IKr deactivation time course compared to adult myocytes.
The study identifies developmental differences in the delayed rectifying outward potassium current between neonatal and adult feline ventricular myocytes, suggesting differences in I(Kr) subunit composition.
In the present work, we found that the delayed rectifying outward potassium current (I(K)) in adult and neonatal cat ventricular myocytes consists of both rapid and slow components, I(Kr) and I(Ks), respectively, which can be isolated pharmacologically. Thus after complete blockade of I(Kr) with dofetilide, the remaining I(Ks) current is homogeneous, as shown by an envelope of tails test. I(Kr) maximum tail current density, measured at -40 mV, was similar in adult and neonatal myocytes. I(Ks) maximum tail current density in neonatal myocytes, measured at -40 mV, was significantly smaller than in adult myocytes. Activation kinetics of I(Kr) and I(Ks) was similar in both age groups. However, the I(Kr) deactivation time course was significantly faster in neonatal than in adult myocytes. Developmental differences in the subunit composition of I(Kr) that display distinctly different deactivation kinetics are suggested.
Barajas-Martínez et al. (Tue,) conducted a other in Feline ventricular myocytes. Developmental stage (neonatal vs adult) vs. Adult feline ventricular myocytes was evaluated on Delayed rectifying outward potassium current (IKr and IKs) characteristics. Neonatal feline ventricular myocytes exhibited significantly smaller IKs maximum tail current density and faster IKr deactivation time course compared to adult myocytes.