Lysophosphatidylcholine and sodium-calcium exchange in cardiac sarcolemma: comparison with ischemia

1991 ◽  
Vol 260 (3) ◽  
pp. C433-C438 ◽  
Author(s):  
M. M. Bersohn ◽  
K. D. Philipson ◽  
R. S. Weiss
Keyword(s):  
Phospholipase A2 ◽  
Phospholipid Composition ◽  
Maximum Velocity ◽  
Passive Permeability ◽  
Cardiac Sarcolemma ◽  
Sodium Calcium ◽  
Calcium Exchange ◽  
Sarcolemmal Vesicles ◽  
In Vitro Treatment

Lysophosphoglyceride accumulation in ischemic myocardium has been hypothesized to be a mechanism for altered sarcolemmal properties that underlie electrophysiological changes and Ca2+ accumulation in ischemia. We find that in vitro application of lysophosphatidylcholine to normal canine sarcolemmal vesicles at a concentration of 0.3 mumol/mg sarcolemmal protein inhibits Na(+)-Ca2+ exchange. Both maximum velocity (Vmax) for Ca2+ transport and Ca2+ affinity are reduced by lysophosphatidylcholine, whereas in ischemia only Vmax is reduced [M. M. Bersohn, K. D. Philipson, and J. Y. Fukushima. Am. J. Physiol. 242 (Cell Physiol. 11): C288-C295, 1982]. This amount of lysophosphatidylcholine does not affect sarcolemmal passive permeability to either Ca2+ or Na+. Treatment of sarcolemma with phospholipase A2 sufficient to inhibit Na(+)-Ca2+ exchange velocity by 50% causes large increases in sarcolemmal lysophosphatidylcholine and lysophosphatidylethanolamine. On the other hand, 1 h of ischemia in rabbit hearts does not affect sarcolemmal phospholipid composition. Thus, although in vitro treatment with lysophosphatidylcholine or phospholipase A2 has profound effects on sarcolemmal properties, sarcolemmal accumulation of lysophosphatidylcholine cannot account for the effects of ischemia as measured in highly purified sarcolemmal vesicles from ischemic hearts.

Sodium-calcium exchange and sarcolemmal enzymes in ischemic rabbit hearts

1982 ◽  
Vol 242 (5) ◽  
pp. C288-C295 ◽  
Author(s):  
M. M. Bersohn ◽  
K. D. Philipson ◽  
J. Y. Fukushima
Keyword(s):  
Myocardial Ischemia ◽  
Adenylate Cyclase ◽  
Membrane Structure ◽  
Passive Permeability ◽  
Crude Homogenate ◽  
Sodium Calcium ◽  
Ischemic Tissue ◽  
Calcium Exchange ◽  
Time Periods ◽  
Sarcolemmal Vesicles

We have investigated alterations in sarcolemmal function that occur during myocardial ischemia. Rabbit ventricles were incubated at 37 degrees C for time periods ranging from 5 min to 2 h. The ischemic tissue was homogenized, and activities of the sarcolemmal enzymes Na+-K+-ATPase, K+-p-nitrophenylphosphatase (K+-pNPPase), and adenylate cyclase were measured in the crude homogenate. Na+-K+-ATPase and K+-pNPPase were substantially inhibited after only 10 min of ischemia, and activities for all three enzymes declined progressively up to 1 h of ischemia, when activities were 37–59% of control. Highly purified sarcolemmal membranes prepared from control tissue and myocardium that had been made ischemic for 1 h showed similar purification of sarcolemmal enzymes, passive Ca2+ binding, and passive permeability to Ca2+. However, the velocity of Na+-Ca2+ exchange in ischemic sarcolemmal vesicles was reduced approximately 50% due to a reduction in Vmax. Although the parallel decline in activities of several sarcolemmal functions might suggest a change in membrane structure, phospholipid and cholesterol contents in ischemic sarcolemma were the same as control.

Mechanisms of endotoxin-induced impairment in Na+-Ca2+ exchange in canine myocardium

1986 ◽  
Vol 251 (6) ◽  
pp. R1078-R1085
Author(s):  
M. S. Liu ◽  
Y. T. Xuan
Keyword(s):  
Phospholipase A2 ◽  
Cardiac Sarcolemma ◽  
Endotoxin Administration ◽  
Control Heart ◽  
22Na Uptake ◽  
Inside Out ◽  
In Vivo Administration ◽  
Sarcolemmal Vesicles ◽  
Canine Myocardium

Effects of endotoxin administration on the Na+-Ca2+ exchange in canine cardiac sarcolemma were characterized. In addition, roles of phospholipase A2 and phosphorylation on the endotoxin-induced impairment in Na+-Ca2+ exchange were investigated. The results show that intravesicular sodium (Nai+)-dependent 45Ca2+ uptake was decreased by 39-66% (P less than 0.05) and extravesicular sodium (Nao+)-induced 45Ca2+ efflux was decreased by 36-52% (P less than 0.05) at 2 h following endotoxin administration. Ca2+o-induced 45Ca2+ efflux in the absence of Ko+ was not affected, but Ca2+o-induced 45Ca2+ efflux in the presence of Ko+ was significantly reduced by endotoxin administration. The stoichiometry of Na+-Ca2+ exchange was altered from 3 Na+ for 1 Ca2+ for the control to 2 Na+ for 1 Ca2+ for the endotoxin-treated dogs. The ATP-dependent 22Na+ uptake and Na+-Ca2+ exchange in inside-out vesicles remained unchanged after endotoxin injection. Digestion of control heart sarcolemmal vesicles with exogenous phospholipase A2 (0.02-0.06 unit/500 micrograms protein) inhibited Na+-Ca2+ exchange activity measured as Nai+-dependent 45Ca2+ uptake, and the inhibition was concentration dependent. Lysophosphatidylcholine addition to the control cardiac sarcolemma had no effect on Na+-Ca2+ exchange. The inhibition of Na+-Ca2+ exchange caused by phospholipase A2 digestion in the control heart sarcolemma was completely reversible by the addition of phosphatidylcholine (0.1 mM). The inhibition of Na+-Ca2+ exchange caused by the in vivo administration of endotoxin was completely reversible by the addition of phosphatidylcholine (0.1-0.15 mM).(ABSTRACT TRUNCATED AT 250 WORDS)

Na+-Ca2+ exchange in cardiac sarcolemma: modulation of Ca2+ affinity by exercise

1989 ◽  
Vol 256 (3) ◽  
pp. C638-C643 ◽  
Author(s):  
G. F. Tibbits ◽  
H. Kashihara ◽  
K. O'Reilly
Keyword(s):  
Exercise Training ◽  
Weight Ratio ◽  
Maximum Velocity ◽  
Rapid Quenching ◽  
Group Differences ◽  
Sprague Dawley ◽  
Cardiac Sarcolemma ◽  
Sprague Dawley Rats ◽  
Response To Exercise ◽  
Sarcolemmal Vesicles

The high activity of the cardiac Na+-Ca2+ exchanger has led to the suggestion that it plays an important role in the regulation of myocardial contractility. We have proposed that exercise training increases stroke volume as a consequence of an enhanced contractility caused by an adaptation in Ca2+ transport across the cardiac plasma membrane (sarcolemma). The present study examined the possibility that the Na+-Ca2+ exchanger in heart muscle is modified in response to training. Sprague-Dawley rats (female, n = 72) were randomly divided into exercise-trained (T) and sedentary control (C) groups. As a result of the 11-wk treadmill-training paradigm, group T had a 7.6% higher (P less than 0.005) heart-to-body weight ratio and a 36% increase (P less than 0.01) in gastrocnemius mitochondrial enzyme activity. Na+-Ca2+ exchange was studied in highly purified sarcolemmal vesicles using rapid-quenching techniques. The absolute initial rate of uptake was significantly higher in T vs. C at calcium concentrations [( Ca2+]) ranging from 10 to 80 microM. This increased uptake appears to be due solely to the fact that the apparent Km of the myocardial Na+-Ca2+ exchanger for Ca2+ was significantly lower in T vs. C (15.7 +/- 1.1 vs. 36.1 +/- 2.6 microM), since the maximum velocity was unchanged. The observed increase in the affinity of the exchanger for Ca2+ is not attributable to group differences in vesicular purity, cross-contamination, or passive Ca2+ efflux. This observation is consistent with observed alterations in sarcolemmal composition in response to exercise training. We propose that the modification of the Na+-Ca2+ exchanger may play an important role in the adaptation of the heart to exercise.

scholarly journals TRANSCELLULAR INTESTINAL CALCIUM TRANSPORT IN FRESHWATER AND SEAWATER FISH AND ITS DEPENDENCE ON SODIUM/CALCIUM EXCHANGE

1993 ◽  
Vol 176 (1) ◽  
pp. 195-206 ◽  
Author(s):  
T. J. M. Schoenmakers ◽  
P. M. Verbost ◽  
G. Flik ◽  
S. E. Wendelaar Bonga
Keyword(s):  
Calcium Uptake ◽  
Oreochromis Mossambicus ◽  
Transport Function ◽  
Calcium Gradient ◽  
Sodium Calcium ◽  
Basolateral Plasma Membrane ◽  
Calcium Exchange ◽  
Proximal Intestine ◽  
Exchange Activity

Transepithelial calcium uptake and transcellular calcium uptake mechanisms were compared in the proximal intestine of freshwater- and seawater-adapted tilapia, Oreochromis mossambicus. Stripped intestinal epithelium of seawater fish showed a higher paracellular permeability to calcium in vitro. Net transepithelial calcium uptake was 71 % lower, reflecting a physiological response to the increased inward calcium gradient. Na+/K+-ATPase activity was significantly enhanced in enterocytes of seawater-adapted fish, in line with the water transport function of the intestine in seawater fish. The Vmax and the Km values for Ca2+ of the ATP-dependent Ca2+ pump in seawater fish enterocytes were 28 % and 27 %, respectively, lower than in freshwater fish. The Km for Ca2+ of the Na+/Ca2+ exchanger was 22 % lower, and a 57 % decrease in the Vmax for Ca2+ of the exchanger was observed. Apparently, the density of exchanger molecules in the basolateral plasma membrane is reduced in seawater fish. From the correlation between the differences in net intestinal calcium uptake and Na+/Ca2+ exchange activity we conclude that Na+/Ca2+ exchange is the main basolateral effector of transcellular calcium uptake.

Protein kinase C mediated activation and phosphorylation of Ca2+ pump in cardiac sarcolemma

1992 ◽  
Vol 70 (9) ◽  
pp. 1230-1235 ◽  
Author(s):  
Yi Qu ◽  
Joseph Torchia ◽  
Amar Kumar Sen
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Heart Tissue ◽  
Cardiac Sarcolemma ◽  
Pumping Rate ◽  
Kinase C ◽  
Calcium Affinity ◽  
Intracellular Ca ◽  
Sarcolemmal Vesicles

The effects of purified protein kinase C (PKC) on the Ca2+-pumping ATPase of cardiac sarcolemma were investigated. The addition of PKC to sarcolemmal vesicles resulted in a significant increase in ATP-dependent Ca2+ uptake, by increasing the calcium affinity by 2.8-fold (Km 0.14 vs. 0.4 μM for control) and by increasing Vmax from 5 to 6.8 nmol∙mg protein−1∙min−1. The addition of PKC also stimulated Ca2+ ATPase activity in sarcolemmal preparations. This activity was increased further upon the addition of calmodulin. These results suggest that PKC stimulates Ca2+ ATPase through a kinase-directed phosphorylation. The addition of PKC to a purified preparation of Ca2+ ATPase in the presence of [γ-32P]ATP resulted in a 100% increase in phosphorylation that was dependent on the presence of Ca2+, phosphatidylserine, and phorbol 12,13-dibutyrate. These results demonstrate that the Ca2+ ATPase of canine cardiac muscle can be phosphorylated by PKC in vitro, resulting in increased affinity of the Ca2+ ATPase for Ca2+ and increase in the Ca2+ pump pumping rate. The results suggest that the Ca2+-pumping ATPase in heart tissue can be stimulated by PKC, thereby regulating the intracellular Ca2+ levels in whole heart.Key words: protein kinase C, phosphorylation, plasma membrane, Ca2+ ATPase, heart.

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