%0 Journal Article %1 Yue_1986_223 %A Yue, D. T. %A Marban, E. %A Wier, W. G. %D 1986 %J J. Gen. Physiol. %K 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, 2419483 3-Pyridinecarboxylic Animals, Calcium, Carnivora, Channels, Chemical, Contraction, Ferrets, Gov't, Heart, In Ion Membrane Methyl Muscles, Myocardial Nifedipine, Non-U.S. P.H.S., Papillary Perfusion, Potentials, Research Ryanodine, Stimulation, Support, U.S. Vitro, acid, ester, %N 2 %P 223--242 %T Relationship between force and intracellular Ca$^2+$ in tetanized mammalian heart muscle. %U http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=2419483&query_hl=30 %V 87 %X To determine features of the steady state Ca$^2+$-tension relationship in intact heart, we measured steady force and intracellular Ca$^2+$ (Ca$^2+$i) in tetanized ferret papillary muscles. Ca$^2+$i was estimated from the luminescence emitted by muscles that had been microinjected with aequorin, a Ca$^2+$-sensitive, bioluminescent protein. We found that by raising extracellular Ca$^2+$ and/or by exposing muscles to the Ca$^2+$ channel agonist Bay K 8644, tension development could be varied from rest to an apparently saturating level, at which increases in Ca$^2+$i produced no further rise in force. 95\% of maximal Ca$^2+$-activated force was reached at a Ca$^2+$i of 0.85 +/- 0.06 microM (mean +/- SEM; n = 7), which suggests that the sensitivity of the myofilaments to Ca$^2+$i is far greater than anticipated from studies of skinned heart preparations (or from previous studies using Ca$^2+$-sensitive microelectrodes in intact heart). Our finding that maximal force was reached by approximately 1 microM also allowed us to calculate that the steady state Ca$^2+$i-tension relationship, as it might be observed in intact muscle, should be steep (Hill coefficient of greater than 4), which is consistent with the Hill coefficient estimated from the entire Ca$^2+$i-tension relationship derived from families of variably activated tetani (6.08 +/- 0.68; n = 7). Finally, with regard to whether steady state measurements can be applied directly toward understanding physiological contractions, we found that the relation between steady force and Ca$^2+$i obtained during tetani was steeper than that between peak force and peak Ca$^2+$i observed during physiological twitches.

@article{Yue_1986_223, abstract = {To determine features of the steady state [{C}a$^{2+}$]-tension relationship in intact heart, we measured steady force and intracellular [{C}a$^{2+}$] ([{C}a$^{2+}$]i) in tetanized ferret papillary muscles. [{C}a$^{2+}$]i was estimated from the luminescence emitted by muscles that had been microinjected with aequorin, a {C}a$^{2+}$-sensitive, bioluminescent protein. We found that by raising extracellular [{C}a$^{2+}$] and/or by exposing muscles to the {C}a$^{2+}$ channel agonist Bay K 8644, tension development could be varied from rest to an apparently saturating level, at which increases in [{C}a$^{2+}$]i produced no further rise in force. 95\% of maximal {C}a$^{2+}$-activated force was reached at a [{C}a$^{2+}$]i of 0.85 +/- 0.06 microM (mean +/- SEM; n = 7), which suggests that the sensitivity of the myofilaments to [{C}a$^{2+}$]i is far greater than anticipated from studies of skinned heart preparations (or from previous studies using {C}a$^{2+}$-sensitive microelectrodes in intact heart). Our finding that maximal force was reached by approximately 1 microM also allowed us to calculate that the steady state [{C}a$^{2+}$]i-tension relationship, as it might be observed in intact muscle, should be steep (Hill coefficient of greater than 4), which is consistent with the Hill coefficient estimated from the entire [{C}a$^{2+}$]i-tension relationship derived from families of variably activated tetani (6.08 +/- 0.68; n = 7). Finally, with regard to whether steady state measurements can be applied directly toward understanding physiological contractions, we found that the relation between steady force and [{C}a$^{2+}$]i obtained during tetani was steeper than that between peak force and peak [{C}a$^{2+}$]i observed during physiological twitches.}, added-at = {2009-06-03T11:20:58.000+0200}, author = {Yue, D. T. and Marban, E. and Wier, W. G.}, biburl = {https://www.bibsonomy.org/bibtex/25c09def3394b2aae7a682eb98a55173b/hake}, description = {The whole bibliography file I use.}, file = {Yue_1986_223.pdf:Yue_1986_223.pdf:PDF}, interhash = {e0480d0981d7067aa5fb9503450e9d10}, intrahash = {5c09def3394b2aae7a682eb98a55173b}, journal = {J. Gen. Physiol.}, keywords = {1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, 2419483 3-Pyridinecarboxylic Animals, Calcium, Carnivora, Channels, Chemical, Contraction, Ferrets, Gov't, Heart, In Ion Membrane Methyl Muscles, Myocardial Nifedipine, Non-U.S. P.H.S., Papillary Perfusion, Potentials, Research Ryanodine, Stimulation, Support, U.S. Vitro, acid, ester,}, month = Feb, number = 2, pages = {223--242}, pmid = {2419483}, timestamp = {2009-06-03T11:21:38.000+0200}, title = {Relationship between force and intracellular [{C}a$^{2+}$] in tetanized mammalian heart muscle.}, url = {http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=2419483&query_hl=30}, volume = 87, year = 1986 }