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Ca-ATPase of Human Myometrium Plasma Membranes
F. CARRERA, T. PROVERBIO, R. MARÍN, F. PROVERBIO
Biophysical and Biochemical Center, Venezuelan Institute for Scientific
Investigation, Maternity Hospital ”Concepción Palacios” Caracas, Venezuela
Received July 13, 1999
Accepted November 5, 1999
Summary
We determined and characterized the Mg2+-dependent,
Ca2+-stimulated ATPase (Ca-ATPase) activity in cell plasma membranes
from the myometrium of pregnant women, and compared these characteristics to
those of the active Ca2+-transport already demonstrated in this
tissue. Similarly to the Ca2+-transport system, the Ca2+-ATPase
is Mg2+-dependent, stimulated by calmodulin, and inhibited by vanadate. The Km for Ca2+ activation is 0.40 m
M, very similar to that found for active calcium transport, i.e. 0.25 m
M. Consequently, this Ca2+-ATPase can be responsible for the active
calcium transport across the plasma membranes of smooth muscle cells.
Key words
Calcium adenosine triphosphatase ·
Human myometrium · Smooth muscle.
Reprint requests
Fulgencio Proverbio PhSc, IVIC-CBB, AP 21827, Caracas 1020A,
Venezuela, e-mail: fproverb@cbb.ivic.ve
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