Membrane segregation in atrioventricular nodal myocytes of the golden hamster (Mesocricetus auratus). A cytochemical study using filipin and tomatine.

The membrane systems of hamster general atrial and ventricular myocytes were studied and their reactivity with the sterol probes, filipin and tomatine, compared with that of atrioventricular nodal myocytes. The sarcolemma of atrial and atrioventricular nodal myocytes was considerably more reactive to sterol probes than the sarcolemma of general ventricular myocytes. Atrial myocyte sarcolemma was also more reactive than previously reported in rat atrial myocytes. Particle-free regions of annular nexuses were consistently unreactive with all combinations of sterol probes whereas much smaller particle-free regions of macular nexuses and desmosomes were reactive with the same probes. Intracellular membrane systems of all three types of cardiac myocyte reacted in a similar manner with sterol probes. These results indicate variation in comparable sarcolemma composition of cardiac myocytes between the rat and hamster and between cardiac regions within the same species.