Simultaneous measurements of action potentials and contractions in single cultured adult and embryonic heart muscle cells.

Using both a microphotometrical technique and conventional microelectrodes, excitation and contractions have been measured simultaneously in spontaneously active and electrically driven isolated cultured heart muscle cells of embryonic chicks as well as adult rats and guinea-pigs. This experimental arrangement makes it possible to measure continuously and with high accuracy, excitation and E.C. coupling at the single cell level. The contraction time course of spontaneously active embryonic cells and electrically driven adult cells resembles contractions of macroscopic heart muscle preparations against various preloads; mostly a nearly isometric contraction form is found. The effects of various inotropic factors on excitation and contraction (beat frequency, Ca, epinephrine) were studied and it could be shown that the embryonic cells show different features of E.C. coupling. The activity of adult cells resembles very strongly that characteristically found in macroscopic preparations. This proved the feasibility of the method in studies of cardiac E.C. coupling at the single cell level.