[Mg2+,ATP-dependent transport of Ca2+ in the endoplasmic reticulum of myometrial cells].
An in-depth study of the effects of Ca(2+)-precipitating anions (oxalate, phosphate), the Ca2+ ionophore A23187 and some highly effective selective inhibitors of the endo(sarco)plasmic reticulum Ca(2+)-pump (tapsigargin, cyclopiasonic acid) on ruthenium red (10 microM)-insensitive, Mg2+,ATP-dependent accumulation of Ca2+ in digitonin-permeabilized myometrium cells of nonpregnant estrogen-treated rats, has been carried out. Oxalate and phosphate stimulated Mg2+,ATP-dependent accumulation of Ca2+ in permeabilized smooth muscle cells. The Ca2+ ionophore A23187 (5 microM) added to the medium containing oxalate (10 mM) or phosphate (20 mM) prevented the energy-dependent accumulation of Ca2+. Tapsigargin (50 nM) and cyclopiasonic acid (10 microM) fully suppressed the Mg2+,ATP-dependent Ca2+ increase measured in the presence of the Ca(2+)-precipitating anions. The kinetic data indicate that the tapsigargin affinity for the energy-dependent Ca2+ transporting system is much higher than that of cyclopiasonic acid: Ki app values are 0.9 nM and 0.6 microM, respectively. Oxalate (10 mM) added to the incubation medium initially containing tapsigargin (50 nM) failed to induce the Mg2+,ATP-dependent accumulation of Ca2+ in permeabilized myocytes. The data obtained provide biochemical evidence for the existence in myometrium cells of a Ca(2+)-pump providing the Mg2+,ATP-dependent accumulation of Ca2+ in the nonmitochondrial Ca2+ depot--the endoplasmic reticulum. This reaction is stimulated by precipitating penetrating anions and suppressed by selective inhibitors.
Kosterin
S A
SA
Department of Biochemical Kinetics, National Academy of Sciences of the Ukraine, Kiev.
Babich
L G
LG
Shlykov
S G
SG
Rovenets
N A
NA
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005260:Female; D007211:Indoles / Q000494:pharmacology; D007700:Kinetics; D009130:Muscle, Smooth / Q000166:cytology / Q000378:metabolism; D009215:Myometrium / Q000378:metabolism*; D010070:Oxalates / Q000378:metabolism; D019815:Oxalic Acid; D051381:Rats; D012430:Ruthenium Red / Q000494:pharmacology; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin
D007211:Indoles; D010070:Oxalates; D013729:Terpenes; D012430:Ruthenium Red; D000001:Calcimycin; D019284:Thapsigargin; D000255:Adenosine Triphosphate; D019815:Oxalic Acid; D000252:Calcium-Transporting ATPases; D002118:Calcium; C000543:cyclopiazonic acid
Mg2+,ATP-zavisimyĭ transport Ca2+ v éndoplazmatichesom retikulume kletok miometriia.