Sialic acid at the surface of myocardial cells during embryonic development.

We tested the hypothesis that the reduction of automaticity during the embryonic development of chick ventricular myocytes is correlated with the number of sialic acid residues at the cell surface. The major findings were twofold. First, the sialic acid content of ventricular tissue fragments declined during the period between 4 and 17 days of development; however, when a 26% reduction of cell surface area was taken into account, the surface density of sialic acid at 7 and 17 days was not significantly different. Second, the sialic acid content of ventricular cell aggregates (after 3 days in gyratory culture) increased during the same two-week period. On the surface of these cells, the density was significantly greater at 17 days than at 7 days, even after a 17% increase in cell surface area had been taken into account. When the developmental increase in sialic acid content was compared with a concomitant decline in aggregate beat rates, we calculated a correlation coefficient of 0.85. Thus, while there could be some relationship between aggregate automaticity and sialic acid content, there appears to be no such correlation for fragments of chick ventricle.