Electron probe analysis of cultured vascular smooth muscle

Mitochondrial and cytoplasmic composition were determined with electron probe analysis in freeze‐dried guinea pig aortic smooth muscle cells cultured on stainless steel grids. The mitochondrial calcium content in normal cells was low: not significantly different from that detected in the cytoplasm. Mitochondrial calcium granules were found in less than 3% of the cells, and in these the cytoplasmic K/Na ratio was reduced, indicating that they were damaged. There were no major differences between the cytoplasmic concentrations of K, Cl, Ca, Mg, and S of cultured cells and those previously found in adult vascular smooth muscle (Somlyo et al. '79). There was no evidence of nuclear Na or Ca sequestration in cultured cells, and the transmitochondrial Na, Cl, and K gradients were small. Attempts to selectively remove adhering, extracellular ions with a 2‐second wash with isotonic ammonium acetate were unsuccessful because they were accompanied by loss of cell K.