Oxytocin contracts the human uterus at term by inhibiting the myometrial Ca2+-extrusion pump.
The sarcolemma of smooth-muscle cells from human pregnant myometrium possesses a high-affinity Ca2+-ATPase, which has the characteristics of an active Ca2+-extrusion pump. This pump enzyme, either membrane-bound or solubilized, was strongly inhibited by oxytocin (half-maximal inhibition at about 4 microU/ml or 10 pM). However, under similar conditions, oxytocin did not inhibit Ca2+-extrusion ATPase of the erythrocyte membrane. The inhibitory concentrations of oxytocin correspond to hormone plasma levels which initiate spontaneous labor.
Popescu
L M
LM
Nutu
O
O
Panoiu
C
C
D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002462:Cell Membrane / Q000378:metabolism; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D009215:Myometrium / Q000187:drug effects / Q000378:metabolism*; D010121:Oxytocin / Q000494:pharmacology*; D011247:Pregnancy; D014590:Uterine Contraction / Q000187:drug effects*
D010121:Oxytocin; D000252:Calcium-Transporting ATPases; D002118:Calcium