Uptake and release of calcium by canine gastric corpus smooth muscle plasma membrane enriched fraction

1983 ◽  
Vol 61 (7) ◽  
pp. 699-704 ◽  
Author(s):  
Yasushi Sakai ◽  
Ashok K. Grover ◽  
Jo-Ann E. T. Fox ◽  
Edwin E. Daniel
Keyword(s):  
Smooth Muscle ◽  
Plasma Membrane ◽  
Reaction Time ◽  
Exponential Decay ◽  
Initial Velocity ◽  
Hill Coefficient ◽  
Rapid Loss ◽  
Muscle Plasma Membrane ◽  
Gastric Corpus ◽  
Uptake And Release

Calcium movements across plasma membrane enriched vesicles isolated from canine gastric corpus smooth muscle were investigated. The ATP-dependent Ca2+ uptake increased with time up to 10 min. The uptake for the initial 2-min period was approximately linear with time. The apparent initial velocity of the ATP-dependent Ca2+ uptake increased monotonically with free Ca2+ concentration from 0.1 to 2 μM, and further increases in free Ca2+ concentration did not increase the Ca2+ uptake. The free Ca2+ dependence curve could be described with a Hill coefficient of approximately 1.0 and Km of 0.85 ± 0.01 μM for free Ca2+ concentration. Passive Ca2+ uptake (reaction time = 1 h) also increased with increasing free Ca2+ concentrations from 0.02 to 4.0 mM. Dilution of loaded vesicles in isotonic media containing EGTA led to initial rapid loss (< 1 min) followed by a slower release which showed simple exponential decay. The t1/2 values of the slower Ca2+ loss from these vesicles were 16.1 ± 0.9 min (actively loaded n = 5) and 18.4 ± 0.9 min (passively loaded n = 3), respectively. Dilution in isotonic medium containing both EGTA and A23187 released all the sequestered Ca2+ from these loaded vesicles.

The effects of acetylcholine and atropine on the 22Na+ permeability of intestinal smooth muscle vesicles

1978 ◽  
Vol 56 (6) ◽  
pp. 921-925
Author(s):  
L. Spero
Keyword(s):  
Smooth Muscle ◽  
Plasma Membrane ◽  
Membrane Vesicles ◽  
Intestinal Smooth Muscle ◽  
Erythrocyte Ghosts ◽  
Muscarinic Agonists ◽  
Plasma Membrane Vesicles ◽  
Muscle Plasma Membrane ◽  
Whole Muscle ◽  
Kinetics Of

A technique is described which has enabled us to measure changes in 22Na+ efflux from smooth muscle plasma membrane vesicles. The resting 22Na+ efflux from these sealed vesicles showed a concentration-dependent increase in response to acetylcholine and other muscarinic agonists, in similar concentrations to those which increased 42K+ efflux in whole muscle. The kinetics of this efflux were complex and could not be described by less than three exponential processes. The response to agonists has, therefore, been characterized by measurement of the half-life of 22Na+ efflux (t1/2). The acetylcholine effect was inhibited by atropine, but unlike the situation in the whole muscle, this inhibition was noncompetitive. Tubocuraine (a nicotinic antagonist) had no effect on this acetylcholine response. Atropine has no effect by itself on the resting 22Na+ efflux, neither did tetrodotoxin or ouabain. 22Na+ efflux from erythrocyte ghosts and liposomes, prepared from lipid extracts of the smooth muscle plasma membrane, was not modified by acetylcholine or atropine.

Calcium pump, high-affinity Ca2+-ATPase, and other ATPases in dog antrum smooth muscle plasma membrane

1985 ◽  
Vol 248 (5) ◽  
pp. C449-C456 ◽  
Author(s):  
A. K. Grover ◽  
C. Y. Kwan ◽  
P. J. Oakes
Keyword(s):  
Smooth Muscle ◽  
Plasma Membrane ◽  
Maximal Activity ◽  
Calcium Pump ◽  
Disulfonic Acid ◽  
Calmodulin Antagonists ◽  
High Affinity ◽  
Chelex 100 ◽  
Muscle Plasma Membrane ◽  
Absolute Requirement

The plasma membrane-enriched fraction from dog antrum smooth muscle is enriched in ATP-dependent azide-insensitive Ca2+ uptake (0.3-0.4 microM Ca2+ required for half-maximal activity), a high-affinity Ca2+-ATPase (Km of 0.3-0.8 microM for Ca2+), a low-affinity Ca2+-ATPase (Km for 250-400 microM for Ca2+), and a Mg2+-ATPase. Studies using membranes washed with EDTA and assay media treated with Chelex 100 showed that the high-affinity Ca2+-ATPase did not depend on contaminating Mg2+. Thus, whereas the ATP-dependent Ca2+ uptake had an absolute requirement for Mg2+, the Ca2+-ATPases did not. Studies using gamma-irradiation showed that the protein responsible for the ATP-dependent Ca2+ uptake was inactivated at significantly lower doses of radiation than the three ATPases. The Ca2+ uptake and the high-affinity Ca2+-ATPase also differed in their inhibition by calmodulin antagonists and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid. Thus it is unlikely that the high-affinity Ca2+-ATPase by itself is responsible for the ATP-dependent Ca2+ uptake.

Preferential support of Ca 2+ uptake in smooth muscle plasma membrane vesicles by an endogenous glycolytic cascade

1989 ◽  
Vol 3 (11) ◽  
pp. 2298-2301 ◽  
Author(s):  
Richard J. Paul ◽  
Christopher D. Hardin ◽  
Luc Raeymaekers ◽  
Frank Wuytack ◽  
Rik Casteels
Keyword(s):  
Smooth Muscle ◽  
Plasma Membrane ◽  
Membrane Vesicles ◽  
Plasma Membrane Vesicles ◽  
Muscle Plasma Membrane
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