Spontaneously hypertensive rats and platelet Ca(2+)-ATPases: specific up-regulation of the 97 kDa isoform.
The use of platelets instead of smooth muscle cells (SMC) to study the abnormal Ca2+ handling found in hypertension was investigated using spontaneously hypertensive rats (SHR). We studied the regulation of platelet Ca(2+)-ATPases, as we have recently demonstrated that human platelets, like SMC, contain the Ca(2+)-ATPase isoform termed SERCA2-b (sarco-endoplasmic reticulum Ca(2+)-ATPase). In mixed membranes isolated from platelets of normotensive Wistar-Kyoto (WKY) rats and SHR, total Ca(2+)-ATPase activity was found to be 43% higher in SHR than in WKY rats. By the use of autophosphorylation of rat platelet Ca(2+)-ATPases with [gamma-32P]ATP, followed by SDS/PAGE and Western blotting, we found that rat platelets express two distinct Ca(2+)-ATPases: a 100 kDa isoform, recognized by a SERCA2-b-specific anti-peptide antibody, and a 97 kDa isoform, specifically recognized by a polyclonal anti-SERCA antibody. Comparative analysis of platelet membrane Ca(2+)-ATPases from WKY rats and SHR demonstrated that the expression of the SERCA2-b isoform did not change significantly (128 +/- 22%), whereas that of the 97 kDa isoform reached 300 +/- 35% in SHR when compared with WKY rats. We concluded that the upregulation of total platelet Ca(2+)-ATPases in SHR is not due to the 100 kDa SERCA2-b isoform found in SMC, but is specific to the 97 kDa Ca(2+)-ATPase isoform which is not present in SMC. Therefore platelets should be used with extreme caution as a surrogate model of vascular smooth muscle Ca2+ homeostasis.
Papp
B
B
U. 348 INSERM, Hôpital Lariboisière, Paris, France.
Corvazier
E
E
Magnier
C
C
Kovàcs
T
T
Bourdeau
N
N
Lévy-Tolédano
S
S
Bredoux
R
R
Lévy
B
B
Poitevin
P
P
Lompré
A M
AM
D000818:Animals; D001792:Blood Platelets / Q000201:enzymology*; D015153:Blotting, Western; D000252:Calcium-Transporting ATPases / Q000097:blood*; D002462:Cell Membrane / Q000201:enzymology; D004721:Endoplasmic Reticulum / Q000201:enzymology; D006973:Hypertension / Q000201:enzymology*; D007700:Kinetics; D008970:Molecular Weight; D009130:Muscle, Smooth / Q000201:enzymology; D010766:Phosphorylation; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY
D000252:Calcium-Transporting ATPases