Isolation of Sarcolemmal Membranes from Smooth Muscle
Smooth muscle tone is dependent on cytoplasmic free Ca2+ concentration, which is regulated by Ca2+ influx and efflux across the sarcolemma and across the membranes of intracellular Ca2+-transporting organelles. These Ca2+ transport processes may be altered by changes in ionic composition, hormonal stimulation, pharmacological treatments, and by disease conditions. The movements of Ca2+ in smooth muscle tissues can be studied by measuring the influx and efflux of 45Ca2+ under different experimental conditions, but the interpretation of these data is difficult because of the limited knowledge of compartmentalization of cellular Ca2+. Another approach is to isolate membrane vesicles in purified form and to study Ca2+ transport in vitro to gain an insight into its function in vivo. Since the number of smooth muscle cells is small, and they are usually surrounded by nonmuscle cells, it is difficult to isolate substantial amounts of purified subcellular membranes from smooth muscle tissues. In this chapter, a procedure is described that has been found useful in our laboratory for the isolation of reasonable amounts of sarcolemmal membranes from rat myometrium, pig coronary arteries, and dog and rat mesenteric arteries.
KeywordsWheat Germ Agglutinin Nucleotidase Activity Smooth Muscle Tissue Monoamine Oxidase Activity Sarcolemmal Membrane
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