title: Characterization of Ca2+ transport and enzyme activity in microsomes isolated from guinea-pig stomach smooth muscle.
abstract: Ca2+ uptake by microsomes prepared from guinea-pig stomach required the presence of both ATP and Mg2+ and was unaffected by NaN3. ATP-dependent Ca2+ uptake increased with increasing free Ca2+ concentration from 0.1 to 5 microM, and further increase in Ca2+ concentration above 5 microM did not enhance the uptake further. Half-saturation occurred at approximately 0.55 microM. The t1/2 values of Ca2+ loss from these vesicles loaded in the presence of oxalate were significantly slower than those in the absence of oxalate. Enzyme activity suggested linkage between Ca2+ uptake and ATPase activity, and most of the azide-sensitive component of ATP hydrolysis was attributable to potent inhibition of ADPase activity.
authors.forename: M
authors.initials: M
authors.lastname: Miyagawa
authors.forename: Y
authors.initials: Y
authors.lastname: Sakai
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001386:Azides / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D017301:Ca(2+) Mg(2+)-ATPase; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D005753:Gastric Mucosa / Q000378:metabolism; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D008861:Microsomes / Q000201:enzymology / Q000378:metabolism*; D009130:Muscle, Smooth / Q000201:enzymology / Q000378:metabolism*; D010070:Oxalates / Q000494:pharmacology; D012503:Saponins / Q000494:pharmacology; D019810:Sodium Azide; D013270:Stomach / Q000201:enzymology
chemical_list: D001386:Azides; D010070:Oxalates; D012503:Saponins; D000255:Adenosine Triphosphate; D019810:Sodium Azide; D000251:Adenosine Triphosphatases; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D002118:Calcium