scholarly journals Oxytocin regulates the plasma membrane Ca2+ transport in rat myometrium

1989 ◽  
Vol 261 (1) ◽  
pp. 23-28 ◽  
Author(s):  
A Enyedi ◽  
J Brandt ◽  
J Minami ◽  
J T Penniston
Keyword(s):  
Plasma Membrane ◽  
Sarcoplasmic Reticulum ◽  
Inhibitory Action ◽  
Calcium Uptake ◽  
Membrane Vesicles ◽  
Young Female ◽  
Female Rats ◽  
Maximal Velocity ◽  
Percoll Gradient ◽  
Plasma Membrane Vesicles

Development of myometrium in young female rats was stimulated by administration of diethylstilboestrol. Plasma membrane and sarcoplasmic reticulum from rat myometrium were separated by a new and rapid method using a Percoll gradient. Calcium uptake was inhibited in plasma membrane vesicles isolated from oxytocin-treated myometrium, while no consistent effect of oxytocin was found on the Ca2+ uptake in the sarcoplasmic reticulum. Oxytocin regulated the plasma membrane Ca2+ pump by decreasing its apparent affinity for Ca2+ without affecting its maximal velocity. The K1/2 for Ca2+ in the absence of calmodulin was 0.41 +/- 0.04 microM in normal membranes; this was increased to 0.93 +/- 0.12 microM in oxytocin-treated membranes. Calmodulin decreased the K1/2 for Ca2+ to 0.27 +/- 0.027 microM and oxytocin also increased this, to 0.46 +/- 0.061 microM. The effect of oxytocin on the plasma membrane Ca2+ pump was highly dependent on the hormonal status of the animals. When the diethylstilboestrol was administered together with progesterone, the inhibitory action of oxytocin was totally suppressed, consistent with the expected action of this agent. The results suggest that regulation of the plasma membrane Ca2+ pump may be important in the prolonged elevation of intracellular Ca2+ caused by oxytocin.

Serotonin transport and fluidity in plasma membrane vesicles: effect of hyperoxia

1988 ◽  
Vol 254 (6) ◽  
pp. C781-C787 ◽  
Author(s):  
N. P. Sheridan ◽  
E. R. Block
Keyword(s):  
Endothelial Cells ◽  
Plasma Membrane ◽  
Pulmonary Artery ◽  
Membrane Fluidity ◽  
Fluorescence Probe ◽  
Membrane Vesicles ◽  
Phase System ◽  
Maximal Velocity ◽  
Plasma Membrane Vesicles ◽  
Plasma Membrane Fluidity

Plasma membrane vesicles were prepared from porcine pulmonary artery endothelial cells by a dextran-polyethylene glycol two-phase system. Specific carrier-mediated transport of 5-hydroxytryptamine (5-HT) into the vesicles was examined. Transport required a Na+ gradient (out greater than in) across the membrane, and accumulated 5-HT rapidly effluxed out of the vesicles when the ionophore gramicidin was added. Transport was inhibited by the antidepressant imipramine. 5-HT transport into plasma membrane vesicles appeared saturable and exhibited Michaelis-Menten kinetics (Km 7.4 microM, maximal velocity 217 pmol.min-1.mg membrane protein-1). A 24-h exposure to 95% O2 at 1 atmosphere absolute resulted in a 21% decrease (P less than 0.05) in specific 5-HT transport by plasma membrane vesicles. Hyperoxia also caused a significant (P less than 0.01) decrease in plasma membrane fluidity, as measured with the fluorescence probe 1,6-diphenyl-1,3,5-hexatriene. These results indicate that pulmonary artery endothelial cell plasma membrane vesicles provide a good model for studying 5-HT transport activity in vitro. Hyperoxia affects plasma membrane fluidity and 5-HT transport in pulmonary artery endothelial cells, suggesting a possible cause-and-effect relationship between the two.

scholarly journals Characteristics of the Ca2+ pump and Ca2+-ATPase in the plasma membrane of rat myometrium

1988 ◽  
Vol 252 (1) ◽  
pp. 215-220 ◽  
Author(s):  
A Enyedi ◽  
J Minami ◽  
A J Caride ◽  
J T Penniston
Keyword(s):  
Plasma Membrane ◽  
Atpase Activity ◽  
Calcium Uptake ◽  
Limited Proteolysis ◽  
Membrane Vesicles ◽  
Calcium Pump ◽  
Ionophore A23187 ◽  
Plasma Membrane Vesicles ◽  
Active Calcium ◽  
Stimulation Of

A plasma membrane-enriched fraction from rat myometrium shows ATP-Mg2+-dependent active calcium uptake which is independent of the presence of oxalate and is abolished by the Ca2+ ionophore A23187. Ca2+ loaded into vesicles via the ATP-dependent Ca2+ uptake was released by extravesicular Na+. This showed that the Na+/Ca2+ exchange and the Ca2+ uptake were both occurring in plasma membrane vesicles. In a medium containing KCl, vanadate readily inhibited the Ca2+ uptake (K1/2 5 microM); when sucrose replaced KCl, 400 microM-vanadate was required for half inhibition. Only a slight stimulation of the calcium pump by calmodulin was observed in untreated membrane vesicles. Extraction of endogenous calmodulin from the membranes by EGTA decreased the activity and Ca2+ affinity of the calcium pump; both activity and affinity were fully restored by adding back calmodulin or by limited proteolysis. A monoclonal antibody (JA3) directed against the human erythrocyte Ca2+ pump reacted with the 140 kDa Ca2+-pump protein of the myometrial plasma membrane. The Ca2+-ATPase activity of these membranes is not specific for ATP, and is not inhibited by mercurial agents, whereas Ca2+ uptake has the opposite properties. Ca2+-ATPase activity is also over 100 times that of calcium transport; it appears that the ATPase responsible for transport is largely masked by the presence of another Ca2+-ATPase of unknown function. Measurements of total Ca2+-ATPase activity are, therefore, probably not directly relevant to the question of intracellular Ca2+ control.

Calcium Uptake in Isolated Hepatic Plasma-Membrane Vesicles

1982 ◽  
Vol 129 (1) ◽  
pp. 7-12 ◽  
Author(s):  
Naomi KRAUS-FRIEDMANN ◽  
Jurg BIBER ◽  
Heini MURER ◽  
Ernesto CARAFOLI
Keyword(s):  
Plasma Membrane ◽  
Calcium Uptake ◽  
Membrane Vesicles ◽  
Plasma Membrane Vesicles

scholarly journals Comparison of endogenous and exogenous sources of ATP in fueling Ca2+ uptake in smooth muscle plasma membrane vesicles.

1992 ◽  
Vol 99 (1) ◽  
pp. 21-40 ◽  
Author(s):  
C D Hardin ◽  
L Raeymaekers ◽  
R J Paul
Keyword(s):  
Smooth Muscle ◽  
Plasma Membrane ◽  
Calcium Uptake ◽  
Membrane Vesicles ◽  
Glycolytic Enzyme ◽  
Calcium Pump ◽  
Bulk Solution ◽  
Plasma Membrane Vesicles ◽  
Atp Production ◽  
Muscle Plasma Membrane

A smooth muscle plasma membrane vesicular fraction (PMV) purified for the (Ca2+/Mg2+)-ATPase has endogenous glycolytic enzyme activity. In the presence of glycolytic substrate (fructose 1,6-diphosphate) and cofactors, PMV produced ATP and lactate and supported calcium uptake. The endogenous glycolytic cascade supports calcium uptake independent of bath [ATP]. A 10-fold dilution of PMV, with the resultant 10-fold dilution of glycolytically produced bath [ATP] did not change glycolytically fueled calcium uptake (nanomoles per milligram protein). Furthermore, the calcium uptake fueled by the endogenous glycolytic cascade persisted in the presence of a hexokinase-based ATP trap which eliminated calcium uptake fueled by exogenously added ATP. Thus, it appears that the endogenous glycolytic cascade fuels calcium uptake in PMV via a membrane-associated pool of ATP and not via an exchange of ATP with the bulk solution. To determine whether ATP produced endogenously was utilized preferentially by the calcium pump, the ATP production rates of the endogenous creatine kinase and pyruvate kinase were matched to that of glycolysis and the calcium uptake fueled by the endogenous sources was compared with that fueled by exogenous ATP added at the same rate. The rate of calcium uptake fueled by endogenous sources of ATP was approximately twice that supported by exogenously added ATP, indicating that the calcium pump preferentially utilizes ATP produced by membrane-bound enzymes.

Prolactin increases mRNA encoding Na(+)-TC cotransport polypeptide and hepatic Na(+)-TC cotransport

1995 ◽  
Vol 268 (1) ◽  
pp. G11-G17 ◽  
Author(s):  
Y. Liu ◽  
T. Ganguly ◽  
J. F. Hyde ◽  
M. Vore
Keyword(s):  
Plasma Membrane ◽  
Steady State ◽  
Membrane Vesicles ◽  
Constant Infusion ◽  
Maximal Velocity ◽  
Plasma Membrane Vesicles ◽  
Ovx Rats ◽  
Basolateral Plasma Membrane ◽  
Steady State Levels ◽  
Inhibitor Of Protein Synthesis

We have shown that prolactin (Prl) increases the transhepatic transport of taurocholate (TC) in postpartum rats and following treatment of ovariectomized (Ovx) rats with ovine Prl (oPrl). The present studies were designed to determine if treatment of Ovx rats with oPrl (100, 300, or 600 micrograms/day, 7 days iv) 1) increases Na(+)-TC cotransport in basolateral plasma membrane vesicles (bLPM), 2) induces a corresponding increase in the steady-state levels of Na(+)-TC cotransport polypeptide (Ntcp mRNA), and 3) if the oPrl-mediated increase in Na(+)-TC cotransport activity is blocked by cycloheximide, an inhibitor of protein synthesis. oPrl (300 micrograms/day) induced a twofold increase in the maximal velocity for Na(+)-TC cotransport in both hepatocytes and bLPM vesicles with little change in the Michaelis constant. Infusion of oPrl at a dose of 100, 300, or 600 micrograms/day increased steady-state Ntcp mRNA four-, ten-, and twofold, respectively. Finally, cycloheximide blocked the oPrl-mediated increase in Na(+)-TC cotransport but did not affect basal activity. These data support the hypothesis that an increase in Ntcp mRNA followed by increased synthesis and incorporation of Ntcp in the plasma membrane is responsible for the oPrl-mediated increase in Na(+)-TC cotransport in the basolateral plasma membrane domain of the hepatocyte.

Carrier-mediated transport of tetrabromosulfonephthalein by rat liver plasma membrane vesicles

1992 ◽  
Vol 263 (3) ◽  
pp. G338-G344 ◽  
Author(s):  
A. M. Torres ◽  
J. V. Rodriguez ◽  
G. C. Lunazzi ◽  
C. Tiribelli
Keyword(s):  
Plasma Membrane ◽  
Rat Liver ◽  
Membrane Vesicles ◽  
Hepatic Uptake ◽  
Maximal Velocity ◽  
Plasma Membrane Vesicles ◽  
Liver Plasma Membrane ◽  
Cell Plasma ◽  
Carrier Mediated Transport ◽  
Charged Form

To investigate the molecular requirements and mechanisms for the hepatic uptake of phthaleins, the transport of tetrabromosulfonephthalein (TBS) was investigated in basolateral rat liver plasma membrane vesicles. TBS uptake was electrogenic as greatly accelerated by the creation of a positive-inside membrane potential by the addition of valinomycin in the presence of an inwardly directed potassium gradient. No effect was observed when the ionophore was added in the presence of a sodium gradient. The transport occurred into an osmotic-sensitive space and was saturable with an apparent Michaelis constant of 5.32 +/- 0.56 microM and a maximal velocity of 9.23 +/- 0.25 nmol.s-1.mg protein-1 (mean +/- SD, n = 3 experiments). TBS uptake was directly related to the extra-vesicular pH, indicating the deprotonated quinoid negative-charged form of the dye as the transported species. In contrast, TBS uptake was inversely related to the intravesicular pH, suggesting that protonation inside the vesicles may act as an efficient trap in transport process. Addition of polyclonal monospecific anti-bilitranslocase antibody to liver vesicles specifically inhibited TBS uptake rate (3.27 +/- 0.17 vs. 5.82 +/- 0.61 nmol.s-1.mg protein-1, n = 3, P less than 0.001). These data indicate that TBS is electrogenically transported across the liver cell plasma membrane by bilitranslocase. They also indicate that the presence of a negative charged group on the benzenic ring of the ligand is important in accounting for the transport.

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