The relationship between Ca2+-ATPase and freely exchangeable Ca2+ in the dense tubules: a study in platelets from women.
The main aims of this work were to examine in women: the relationship between the freely exchangeable Ca2+ (FECa2+) in the dense tubules and the activity of the sarco(endo)plasmic reticulum (SER) Ca2+-ATPase (SERCA) in platelets, and the relationship of these parameters with blood pressure and serum lipoproteins. Platelets from 14 white and 13 black women in good health were studied. The FECa2+ was measured as the ionomycin-evoked Ca2+ release (in the presence of thapsigargin) in Ca2+-free medium. SERCA activity was measured as the thapsigargin sensitive, Ca2+ dependent and ouabain resistant, ATP hydrolyses in platelet membranes. Relative expressions of SERCA 2 and 3 isoforms and Ras-related protein (Rap) 1 in platelet membranes were determined by Western immunoblots. Highly significant correlations were observed for FECa2+ in the dense tubules with: 1) the maximal reaction velocity (Vmax) of the SERCA (r = 0.592, P = .0014), and 2) Rapl (r = 0.551, P = .0035). In addition, negative correlations were observed between FECa2+ in the dense tubules and age. No correlations were observed for these variables with blood pressure or serum lipoproteins. We conclude the FECa2+ and the Vmax of the SERCA are reliable indicators of Ca2+ load in platelets from women. However, in women, unlike previous observations in men, these platelet parameters are not correlated with blood pressure and serum lipoproteins.
Horiguchi
M
M
Hypertension Research Center, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark 071032-2714, USA.
Kimura
M
M
Lytton
J
J
Poch
E
E
Aviv
A
A
D000328:Adult; D044383:Black People; D001792:Blood Platelets / Q000187:drug effects / Q000201:enzymology*; D001794:Blood Pressure; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000096:biosynthesis* / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D019204:GTP-Binding Proteins / Q000096:biosynthesis / Q000187:drug effects; D006801:Humans; D006973:Hypertension / Q000097:blood; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D008074:Lipoproteins / Q000097:blood; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000201:enzymology*; D014157:Transcription Factors / Q000096:biosynthesis / Q000187:drug effects; D044465:White People; D020668:rap GTP-Binding Proteins
D004791:Enzyme Inhibitors; D007476:Ionophores; D008074:Lipoproteins; D014157:Transcription Factors; D015759:Ionomycin; D019204:GTP-Binding Proteins; D020668:rap GTP-Binding Proteins; D000252:Calcium-Transporting ATPases; D002118:Calcium