L-Type Calcium Current in Pediatric and Adult Human Atrial Myocytes: Evidence for Developmental Changes in Channel Inactivation

Abstract

Animal studies have documented the presence of marked, species-dependent, developmental changes in the properties of the L-type calcium current in cardiac myocytes. In an effort to understand the postnatal changes which occur in the calcium current in human heart, we characterized the calcium current in atrial myocytes isolated from 17 pediatric and older children (ages 3 d to 14 y) and 12 adult (ages 43-79 y) human hearts using the whole-cell patch clamp technique. In contrast to animal models, we found no evidence for age-related changes in calcium current density, steady-state inactivation, or kinetics of recovery from inactivation, suggesting that, in human atrium, calcium channels are in many aspects functionally mature at the time of birth. However, statistically significant differences were found in the kinetics of calcium current inactivation, with calcium current measured in cells isolated from pediatric human atria inactivating approximately 2-fold faster than cells isolated from adult hearts. These results suggest a possible role for age-related changes in calcium current inactivation in the shortened action potential duration observed in pediatric compared with adult human atrium.