Erythrocyte membrane calcium adenosine 5'-triphosphatase activity in the spontaneously hypertensive rat.
1. Ca2+-adenosine 5'-triphosphatase (Ca2+-Mg2+-ATPase) activity was studied simultaneously in calmodulin-deficient erythrocyte ghost membranes and inside-out vesicles (IOVs) from 12-week-old female spontaneously hypertensive rats (SHR) and their matched controls: [Wistar-Kyoto normotensive rats (WKY)], and in detergent extracts of ghost membranes. 2. Both adenosine 5'-triphosphate (ATP)-dependent Ca2+ uptake by IOVs and Ca2+-dependent ATP hydrolysis activity of ghost membranes were reduced significantly in the SHR compared with WKY, when either the calmodulin-independent or calmodulin-stimulated activities were compared. 3. The ratios between Ca2+ uptake and ATP hydrolysis activities in the SHR remained approximately 1.0, showing a proportional reduction in both activities. 4. No difference in affinity for calmodulin was observed between SHR and WKY. 5. No significant difference in Ca2+-dependent ATP hydrolysis activity was observed between SHR and WKY after detergent solubilization of erythrocyte ghost membranes. 6. These results suggest that the number of Ca2+-Mg2+-ATPase units are similar in SHR and WKY and that the reduced activity in the intact SHR membrane is due to altered membrane environment.
Adeoya
A S
AS
Department of Medicine, University of Leicester, Leicester Royal Infirmary, U.K.
Norman
R I
RI
Bing
R F
RF
D000818:Animals; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism; D004910:Erythrocyte Membrane / Q000201:enzymology*; D005260:Female; D006973:Hypertension / Q000201:enzymology*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY
D002147:Calmodulin; D000252:Calcium-Transporting ATPases; D002118:Calcium