Plasma membrane derived from the myometrial tissues of pregnant and non-pregnant rats accumulates Ca2+ both by Na+ and by ATP-dependent ways. Sodium-dependent Ca2+-uptake in plasma membranes obtained from 20 days pregnant rats reveals higher Ca2+ sensitivity than in plasma membrane of non-pregnant rats. Ca2+ concentration required for half maximal Ca2+-transport was 5.7 ± 0.5 /μM and 11.8 ± 0.6 /μM in plasma membrane of pregnant and non-pregnant rats, respectively. The initial rate of sodium-dependent Ca2+-uptake also differed in membrane preparations from pregnant and non-pregnant animals. ATP-dependent Ca2+-uptake in myometrial plasma membrane of pregnant rats was higher than in non-pregnant ones. The difference was abolished by calmodulin antagonist drugs. In calmodulin depleted preparations the administration of exogenous calmodulin restored Ca2+-uptake to the rate measured in calmodulin not-depleted ones. Membrane phosphorylation by endogenous protein kinases proved to be also different in the two preparations.
|Journal||Biomedica Biochimica Acta|
|Publication status||Published - Jan 1 1989|
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