%0 Journal Article %1 Post_1992_49 %A Post, J. A. %A Langer, G. A. %D 1992 %J J. Membr. Biol. %K 1-Propanol, 1404340 Animals, Binding C, Calcium Calcium, Cell Cells, Compartmentation, Cultured, Dissection, Endopeptidases, Gov't, Lanthanum, Models, Myocardium, Neuraminidase, Newborn, Nifedipine, Nitrogen, Non-U.S. P.H.S., Phospholipase Phospholipids, Radioisotopes, Rats, Research Reticulu, Ryanodine, Sarcolemma, Sarcoplasmic Sites, Support, Terpenes, Thapsigargin, Theoretical, U.S. m, %N 1 %P 49--57 %R 10.1007/BF00232054 %T Sarcolemmal calcium binding sites in heart: I. Molecular origin in "gas-dissected" sarcolemma. %U http://dx.doi.org/10.1007/BF00232054 %V 129 %X Calcium in the myocardial cell is highly compartmentalized and a fast, an intermediate, a slow and a nonexchangeable calcium pool have been described. The fast pool contains 66\% of the total cell exchangeable calcium in cultured neonatal rat heart cells with a t1/2 of less than 1.5 sec. Though the cellular origin of this fast pool is unknown, its rapidity and its displacement by La3+ most likely places it at the sarcolemma or at least in rapid equilibrium with the sarcolemma. We isolated the sarcolemma of cultured neonatal rat heart cells using the gas-dissection technique, which yields a pure sarcolemmal preparation in less than a second, thereby precluding membrane changes which might occur during conventional plasma membrane isolation. We determined the calcium binding characteristics of these membranes, using an on-line technique to monitor 45Ca, which allows measurement of 45Ca binding characteristics in the presence of unbound 45Ca. Two classes of calcium binding sites were determined: (i) Kd of 13 microM, capacity 7 nmol/mg and (ii) Kd of 1.1 mM, capacity of 84 nmol/mg. To assess the molecular origin of the sarcolemmal calcium binding we treated the membranes with a variety of enzymes. Protease or neuraminidase treatment did not cause large changes in these parameters. Simultaneous treatment with two different phospholipases C or the extraction of the lipids with isopropanol resulted in a dramatic loss of the low-affinity binding sites. These results, in association with previously defined sarcolemmal phospholipid distribution, places the low-affinity binding sites at the cytoplasmic leaflet. The physiological implication of this localization as it pertains to cellular calcium exchange is discussed.

@article{Post_1992_49, abstract = {Calcium in the myocardial cell is highly compartmentalized and a fast, an intermediate, a slow and a nonexchangeable calcium pool have been described. The fast pool contains 66\% of the total cell exchangeable calcium in cultured neonatal rat heart cells with a t1/2 of less than 1.5 sec. Though the cellular origin of this fast pool is unknown, its rapidity and its displacement by La3+ most likely places it at the sarcolemma or at least in rapid equilibrium with the sarcolemma. We isolated the sarcolemma of cultured neonatal rat heart cells using the gas-dissection technique, which yields a pure sarcolemmal preparation in less than a second, thereby precluding membrane changes which might occur during conventional plasma membrane isolation. We determined the calcium binding characteristics of these membranes, using an on-line technique to monitor 45Ca, which allows measurement of 45Ca binding characteristics in the presence of unbound 45Ca. Two classes of calcium binding sites were determined: (i) Kd of 13 microM, capacity 7 nmol/mg and (ii) Kd of 1.1 mM, capacity of 84 nmol/mg. To assess the molecular origin of the sarcolemmal calcium binding we treated the membranes with a variety of enzymes. Protease or neuraminidase treatment did not cause large changes in these parameters. Simultaneous treatment with two different phospholipases C or the extraction of the lipids with isopropanol resulted in a dramatic loss of the low-affinity binding sites. These results, in association with previously defined sarcolemmal phospholipid distribution, places the low-affinity binding sites at the cytoplasmic leaflet. The physiological implication of this localization as it pertains to cellular calcium exchange is discussed.}, added-at = {2009-06-03T11:20:58.000+0200}, author = {Post, J. A. and Langer, G. A.}, biburl = {https://www.bibsonomy.org/bibtex/26a4500946e8ad7f676f9fbe60c496922/hake}, description = {The whole bibliography file I use.}, doi = {10.1007/BF00232054}, file = {Post_1992_49.pdf:Post_1992_49.pdf:PDF}, interhash = {edb3fbd3ad6dd5bd18c31bd1635ba96e}, intrahash = {6a4500946e8ad7f676f9fbe60c496922}, journal = {J. Membr. Biol.}, key = 237, keywords = {1-Propanol, 1404340 Animals, Binding C, Calcium Calcium, Cell Cells, Compartmentation, Cultured, Dissection, Endopeptidases, Gov't, Lanthanum, Models, Myocardium, Neuraminidase, Newborn, Nifedipine, Nitrogen, Non-U.S. P.H.S., Phospholipase Phospholipids, Radioisotopes, Rats, Research Reticulu, Ryanodine, Sarcolemma, Sarcoplasmic Sites, Support, Terpenes, Thapsigargin, Theoretical, U.S. m,}, month = Jul, number = 1, pages = {49--57}, pmid = {1404340}, timestamp = {2009-06-03T11:21:26.000+0200}, title = {Sarcolemmal calcium binding sites in heart: I. Molecular origin in "gas-dissected" sarcolemma.}, url = {http://dx.doi.org/10.1007/BF00232054}, volume = 129, year = 1992 }