Comparison of Ca2+-extrusion systems in the myometrial plasma membrane of pregnant and non-pregnant rats.
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 microM and 11.8 +/- 0.6 microM 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.
Vér
A
A
Institute of Biochemistry I., Semmelweis University, Medical School, Budapest, Hungary.
Müllner
N
N
Somogyi
J
J
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001345:Autoradiography; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects* / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D005260:Female; D066298:In Vitro Techniques; D008985:Monensin / Q000494:pharmacology; D009215:Myometrium / Q000378:metabolism*; D010761:Phosphorus Radioisotopes; D011189:Potassium Chloride / Q000494:pharmacology; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000378:metabolism*; D051381:Rats; D012508:Sarcolemma / Q000187:drug effects / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D013997:Time Factors
D015220:Calcium Channels; D010761:Phosphorus Radioisotopes; D011189:Potassium Chloride; D000255:Adenosine Triphosphate; D008985:Monensin; D012964:Sodium; D002118:Calcium