Correlation of function and morphology of neonatal rat and embryonic chick cultured cardiac and vascular muscle cells.

To develop morphological criteria which can be applied systematically for the identification of isolated cardiac and vascular muscle cells in mammalian and avian primary cultures, we have correlated structural and staining properties with excitability, contraction, and norepinephrine sensitivity of isolated muscle cells. The primary cultures of cardiac and vascular muscle contained muscle cells and nonmuscle cells. The muscle cells could be clearly identified by action potentials, contractility, and Masson's trichrome stain characteristics, similar to those of cells from intact source heart and blood vessels. Furthermore, the muscle cells were highly responsive to norepinephrine, showing unequivocal increases in contraction frequency. The sensitivity to norepinephrine was found to be very high (ED50 = 2.3 X 10(-9) M) Phase-contrast observation was sufficient to identify muscle cells only when those cells were contracting. There were no unequivocal morphological characteristics that distinguished between quiescent muscle cells and nonmuscle cells in the absence of histochemical staining. Ultrastructural examination by scanning electron microscopy failed to distinguish between muscle and nonmuscle cells. Histological staining was, therefore, the only reliable nonfunctional identification process that separated muscle cells from nonmuscle cells. Primary cultures, containing nonmuscle as well as muscle cells, are an important experimental preparation because the cellular heterogeneity probably minimizes muscle cell loss of function and phenotypic changes. The correlation we have established between cell staining and function will facilitate exploration of single cell properties, which together constitute hearts and blood vessels.