Suspension of Smooth Muscle Cells Treated with Digitonin as a Model for Studying the Myometrial Endoplasmic Reticulum Calcium Pump

S. G. Shlykov,¹ L. G. Babich,¹ and S. A. Kosterin^1,2

¹Department of Muscle Biochemistry, Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, ul. Leontovicha 9, Kiev-30, 252030 Ukraine; fax: (044) 229-6365; E-mail: KINET@biochem.freenet.Kiev.ua

²To whom correspondence should be addressed.

Submitted June 3, 1997; revision submitted July 24, 1997.

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The effect of the nonionic detergent digitonin on ruthenium red-insensitive, oxalate-stimulated, and thapsigargin-suppressed accumulation of Ca²⁺ by suspension of myometrial cells from ATP- and Mg²⁺-containing incubation medium was studied using passive loading with ⁴⁵Ca²⁺. The dependence of Ca²⁺ accumulation by the cells on the concentration of digitonin is bell-shaped, the maximal Ca²⁺ uptake being observed at 0.05-0.1 mg/ml digitonin. Myocytes chemically skinned with digitonin represent a suitable experimental model for studying kinetic properties of the uterine myocyte endoplasmic reticulum Mg²⁺,ATP-dependent Ca²⁺ pump and assessing sensitivity of this Ca²⁺-transporting system to various effectors including the uterotonic octapeptide oxytocin.

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KEY WORDS: calcium pump, digitonin, ruthenium red, oxalate, thapsigargin, oxytocin, endoplasmic reticulum, smooth muscle cells, myometrium.

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