Na+/Ca2+ exchange current density in cardiac myocytes from rabbits and guinea pigs during postnatal development

Am J Physiol. 1995 Apr;268(4 Pt 2):H1714-22. doi: 10.1152/ajpheart.1995.268.4.H1714.

Abstract

It has been proposed that the activity of the cardiac sarcolemmal Na+/Ca2+ exchanger may be greatest in developing animals before the sarcoplasmic reticulum (SR) reaches functional maturity. Experiments were performed in rabbits, which have a sparse SR at birth, and in newborn guinea pigs, which exhibit a more extensive SR. Whole cell voltage clamp techniques were used to characterize the Ni(2+)-sensitive Na+/Ca2+ exchange current in single freshly isolated cardiac myocytes. Na+/Ca2+ exchange current was measured from a holding potential of -40 mV by using a slow-ramp voltage protocol (-120 to +60 mV, 0.09 V/s) in the presence of Ba2+, Cs+, tetraethylammonia, D-600, and ouabain to block Ca2+, Na+, and K+ currents. Experiments in developing rabbits (1-22 days old) demonstrated that Na+/Ca2+ exchange current density was greatest at 1-4 days and declined rapidly over the first 3 wk of age. In contrast, Na+/Ca2+ exchange current density in newborn guinea pig myocytes did not differ from that recorded in adults. These results confirm that Na+/Ca2+ exchange is functional at birth in both rabbits and guinea pigs. The species-related difference in the ontogeny of Na+/Ca2+ exchange is consistent with the concept that Na+/Ca2+ exchange assumes a relatively greater role in newborn animals with a sparse SR.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Newborn / metabolism*
  • Carrier Proteins / physiology*
  • Electric Conductivity
  • Electrophysiology
  • Guinea Pigs
  • Myocardium / metabolism*
  • Rabbits
  • Sodium-Calcium Exchanger

Substances

  • Carrier Proteins
  • Sodium-Calcium Exchanger