Ultrastructural and cytochemical characterization of subcellular fraction of plasmalemmal origin obtained from uterine longitudinal smooth muscle.
The role of Ca2+-ATPase as the driving force for active calcium uptake, involved in the relaxation of smooth muscle, was studied. It was shown by immunocytochemistry that Ca2+-ATPase activity was localized at the plasma membrane level of longitudinal smooth muscle of pregnant rat uteri (18-20 days). To study calcium regulation in uterine longitudinal smooth muscle, 2 microsomal fractions (F1 and F2) were obtained, enriched in plasma membrane material (Lalanne et al., 1984, in: Calcium Regulation in Smooth Muscles. INSERM series, 124, pp. 283-292). In the present paper this material is characterized at both morphologic and cytochemical levels. Both fractions are ultrastructurally heterogeneous: (a) thin sections clearly show 2 populations that differ in vesicular shape and size; (b) negative staining also shows differences in membrane structure, which could be related to biochemical differences and/or to the well known heterogeneity of the plasma membrane. Two reactions (PATAg and concanavalin A-biotin-avidin-ferritin), allowing visualization of cell coat glycans, were performed on F1 and F2 and on thin sections of longitudinal smooth muscle. Plasma membrane and almost all the vesicles of F1 and F2 are reactive. It is concluded that these 2 fractions are characteristic enough for studying, at the molecular level, the ability of plasma membrane to control calcium circulation in uterine smooth muscle.
D000818:Animals; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002458:Cell Fractionation; D002462:Cell Membrane / Q000201:enzymology* / Q000648:ultrastructure; D005260:Female; D006651:Histocytochemistry; D008854:Microscopy, Electron; D009130:Muscle, Smooth / Q000201:enzymology* / Q000648:ultrastructure; D051381:Rats; D011952:Receptors, Concanavalin A / Q000378:metabolism; D014599:Uterus / Q000201:enzymology* / Q000648:ultrastructure
D011952:Receptors, Concanavalin A; D000252:Calcium-Transporting ATPases