title: ATP-dependent Ca-uptake by rat vas deferens smooth muscle microsomes: properties of oxalate stimulated and oxalate-independent Ca-uptake.
abstract: The oxalate-stimulated and -independent components of the ATP-dependent azide insensitive Ca-uptake by rat vas deferens smooth muscle microsomes differ in the following properties: (a) 5, 5'-disulfonate stilbene (DIDS) and digitonin inhibited the oxalate-independent Ca-uptake more strongly than the oxalate-stimulated component; (b) phosphatidylserine inhibited the oxalate-stimulated Ca-uptake and had no significant effect on the oxalate-independent uptake and (c) digitonin treatment of microsomes changed the density distributions of the two modes differentially. The untreated microsomes gave two Ca-uptake peaks on sucrose density gradients: one at density 1.130 +/- 0.010 g/ml and the other at 1.214 +/- 0.005 g/ml. Digitonin treatment shifted the distribution of the lower density peak to slightly higher density for the oxalate-independent Ca-uptake but not for the oxalate-stimulated Ca-uptake. Distribution of phosphodiesterase I was also shifted to higher densities while distributions of the higher density Ca-uptake peak, NADPH: cytochrome c reductase and of cytochrome c oxidase were not significantly altered. Thus clearly the oxalate-stimulated and the oxalate-independent Ca-uptake in rat vas deferens smooth muscle microsomes show several differences but it is unknown whether the differences are due to the existence of two distinct Ca-pump proteins or due to different microenvironment of the same protein resulting from membrane heterogeneity.
mesh_terms: D000255:Adenosine Triphosphate / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002499:Centrifugation, Density Gradient; D004072:Digitonin / Q000494:pharmacology; D004074:Digitoxin / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism*; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism*; D010070:Oxalates / Q000494:pharmacology*; D019815:Oxalic Acid; D051381:Rats; D013997:Time Factors; D014649:Vas Deferens / Q000187:drug effects / Q000378:metabolism
chemical_list: D002121:Calcium Channel Blockers; D010070:Oxalates; D000255:Adenosine Triphosphate; D019815:Oxalic Acid; D004074:Digitoxin; D004072:Digitonin; D002118:Calcium