We have shown that the sarcoplasmic reticulum develops during the 2nd trimester in human fetal cardiac myocytes. We measured the contribution of Na-Ca exchange to contractions and relaxation in myocyte clusters and ventricular myocytes from 1st and 2nd trimester human fetal hearts, respectively. Studies were performed under the guidelines of IRB protocol # 5754-96. Myocytes were bathed in normal solution at 30° and field-stimulated at 0.25 Hz. Contractions were measured with an edge detector. During the 1st trimester, rapid application of Na-free external solution increased peak contractions and prolonged relaxation compared to baseline. During the 2nd trimester, there was a larger increase in contractions, and smaller change in relaxation. Cardiac Na-Ca exchanger mRNA levels (RT-PCR), increased between 1st and 2nd trimesters: did not change between the 2nd trimester, 3rd trimester and newborn; and decreased post-natally. The Na-Ca exchanger contributes to contractions in human fetal hearts. Inhibition of Na-Ca exchange during the 2nd trimester may have less effect on relaxation because the sarcoplasmic reticulum is functional.
|Original language||English (US)|
|State||Published - Mar 20 1998|
ASJC Scopus subject areas
- Molecular Biology