Expression of slow skeletal troponin I in adult transgenic mouse heart muscle reduces the force decline observed during acidic conditions

Beata M. Wolska; Kalpana Vijayan; Grace M. Arteaga; John P. Konhilas; Ronald M. Phillips; Robert Kim; Taihei Naya; Jeffrey M. Leiden; Anne F. Martin; Pieter P. De Tombe; R. John Solaro

doi:10.1111/j.1469-7793.2001.00863.x

Expression of slow skeletal troponin I in adult transgenic mouse heart muscle reduces the force decline observed during acidic conditions

Beata M. Wolska, Kalpana Vijayan, Grace M. Arteaga, John P. Konhilas, Ronald M. Phillips, Robert Kim, Taihei Naya, Jeffrey M. Leiden, Anne F. Martin, Pieter P. De Tombe, R. John Solaro

Pediatric and Adolescent Medicine

Research output: Contribution to journal › Article › peer-review

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Abstract

1. Acidosis in cardiac muscle is associated with a decrease in developed force. We hypothesized that slow skeletal troponin I (ssTnI), which is expressed in neonatal hearts, is responsible for the observed decreased response to acidic conditions. To test this hypothesis directly, we used adult transgenic (TG) mice that express ssTnI in the heart. Cardiac TnI (cTnI) was completely replaced by ssTnI either with a FLAG epitope introduced into the N-terminus (TG-ssTnI*) or without the epitope (TG-ssTnI) in these mice. TG mice that express cTnI were also generated as a control TG line (TG-cTnI). Non-transgenic (NTG) littermates were used as controls. 2. We measured the force-calcium relationship in all four groups at pH 7.0 and pH 6.5 in detergent-extracted fibre bundles prepared from left ventricular papillary muscles. The force-calcium relationship was identical in fibre bundles from NTG and TG-cTnI mouse hearts, therefore NTG mice served as controls for TG-ssTnI* and TG-ssTnI mice. Compared to NTG controls, the force generated by fibre bundles from TG mice expressing ssTnI was more sensitive to Ca²⁺. The shift in EC₅₀ (the concentration of Ca²⁺ at which half-maximal force is generated) caused by acidic pH was significantly smaller in fibre bundles isolated from TG hearts compared to those from NTG hearts. However, there was no difference in the force-calcium relationship between hearts from the TG-ssTnI* and TG-ssTnI groups. 3. We also isolated papillary muscles from the right ventricle of NTG and TG mouse hearts expressing ssTnI and measured isometric force at extracellular pH 7.33 and pH 6.75. At acidic pH, after an initial decline, twitch force recovered to 60 ± 3% (n = 7) in NTG papillary muscles, 98 ± 2% (n = 5) in muscles from TG-ssTnI* and 96 ± 3% (n = 7) in muscles from TG-ssTnI hearts. Our results indicate that TnI isoform composition plays a crucial role in the determination of myocardial force sensitivity to acidosis.

Original language	English (US)
Pages (from-to)	863-870
Number of pages	8
Journal	Journal of Physiology
Volume	536
Issue number	3
DOIs	https://doi.org/10.1111/j.1469-7793.2001.00863.x
State	Published - Nov 1 2001

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Physiology

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Wolska, B. M., Vijayan, K., Arteaga, G. M., Konhilas, J. P., Phillips, R. M., Kim, R., Naya, T., Leiden, J. M., Martin, A. F., De Tombe, P. P., & Solaro, R. J. (2001). Expression of slow skeletal troponin I in adult transgenic mouse heart muscle reduces the force decline observed during acidic conditions. Journal of Physiology, 536(3), 863-870. https://doi.org/10.1111/j.1469-7793.2001.00863.x

Wolska, BM, Vijayan, K, Arteaga, GM, Konhilas, JP, Phillips, RM, Kim, R, Naya, T, Leiden, JM, Martin, AF, De Tombe, PP & Solaro, RJ 2001, 'Expression of slow skeletal troponin I in adult transgenic mouse heart muscle reduces the force decline observed during acidic conditions', Journal of Physiology, vol. 536, no. 3, pp. 863-870. https://doi.org/10.1111/j.1469-7793.2001.00863.x

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title = "Expression of slow skeletal troponin I in adult transgenic mouse heart muscle reduces the force decline observed during acidic conditions",

abstract = "1. Acidosis in cardiac muscle is associated with a decrease in developed force. We hypothesized that slow skeletal troponin I (ssTnI), which is expressed in neonatal hearts, is responsible for the observed decreased response to acidic conditions. To test this hypothesis directly, we used adult transgenic (TG) mice that express ssTnI in the heart. Cardiac TnI (cTnI) was completely replaced by ssTnI either with a FLAG epitope introduced into the N-terminus (TG-ssTnI*) or without the epitope (TG-ssTnI) in these mice. TG mice that express cTnI were also generated as a control TG line (TG-cTnI). Non-transgenic (NTG) littermates were used as controls. 2. We measured the force-calcium relationship in all four groups at pH 7.0 and pH 6.5 in detergent-extracted fibre bundles prepared from left ventricular papillary muscles. The force-calcium relationship was identical in fibre bundles from NTG and TG-cTnI mouse hearts, therefore NTG mice served as controls for TG-ssTnI* and TG-ssTnI mice. Compared to NTG controls, the force generated by fibre bundles from TG mice expressing ssTnI was more sensitive to Ca2+. The shift in EC50 (the concentration of Ca2+ at which half-maximal force is generated) caused by acidic pH was significantly smaller in fibre bundles isolated from TG hearts compared to those from NTG hearts. However, there was no difference in the force-calcium relationship between hearts from the TG-ssTnI* and TG-ssTnI groups. 3. We also isolated papillary muscles from the right ventricle of NTG and TG mouse hearts expressing ssTnI and measured isometric force at extracellular pH 7.33 and pH 6.75. At acidic pH, after an initial decline, twitch force recovered to 60 ± 3% (n = 7) in NTG papillary muscles, 98 ± 2% (n = 5) in muscles from TG-ssTnI* and 96 ± 3% (n = 7) in muscles from TG-ssTnI hearts. Our results indicate that TnI isoform composition plays a crucial role in the determination of myocardial force sensitivity to acidosis.",

author = "Wolska, {Beata M.} and Kalpana Vijayan and Arteaga, {Grace M.} and Konhilas, {John P.} and Phillips, {Ronald M.} and Robert Kim and Taihei Naya and Leiden, {Jeffrey M.} and Martin, {Anne F.} and {De Tombe}, {Pieter P.} and Solaro, {R. John}",

year = "2001",

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doi = "10.1111/j.1469-7793.2001.00863.x",

language = "English (US)",

volume = "536",

pages = "863--870",

journal = "Journal of Physiology",

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T1 - Expression of slow skeletal troponin I in adult transgenic mouse heart muscle reduces the force decline observed during acidic conditions

AU - Wolska, Beata M.

AU - Vijayan, Kalpana

AU - Arteaga, Grace M.

AU - Konhilas, John P.

AU - Phillips, Ronald M.

AU - Kim, Robert

AU - Naya, Taihei

AU - Leiden, Jeffrey M.

AU - Martin, Anne F.

AU - De Tombe, Pieter P.

AU - Solaro, R. John

PY - 2001/11/1

Y1 - 2001/11/1

N2 - 1. Acidosis in cardiac muscle is associated with a decrease in developed force. We hypothesized that slow skeletal troponin I (ssTnI), which is expressed in neonatal hearts, is responsible for the observed decreased response to acidic conditions. To test this hypothesis directly, we used adult transgenic (TG) mice that express ssTnI in the heart. Cardiac TnI (cTnI) was completely replaced by ssTnI either with a FLAG epitope introduced into the N-terminus (TG-ssTnI*) or without the epitope (TG-ssTnI) in these mice. TG mice that express cTnI were also generated as a control TG line (TG-cTnI). Non-transgenic (NTG) littermates were used as controls. 2. We measured the force-calcium relationship in all four groups at pH 7.0 and pH 6.5 in detergent-extracted fibre bundles prepared from left ventricular papillary muscles. The force-calcium relationship was identical in fibre bundles from NTG and TG-cTnI mouse hearts, therefore NTG mice served as controls for TG-ssTnI* and TG-ssTnI mice. Compared to NTG controls, the force generated by fibre bundles from TG mice expressing ssTnI was more sensitive to Ca2+. The shift in EC50 (the concentration of Ca2+ at which half-maximal force is generated) caused by acidic pH was significantly smaller in fibre bundles isolated from TG hearts compared to those from NTG hearts. However, there was no difference in the force-calcium relationship between hearts from the TG-ssTnI* and TG-ssTnI groups. 3. We also isolated papillary muscles from the right ventricle of NTG and TG mouse hearts expressing ssTnI and measured isometric force at extracellular pH 7.33 and pH 6.75. At acidic pH, after an initial decline, twitch force recovered to 60 ± 3% (n = 7) in NTG papillary muscles, 98 ± 2% (n = 5) in muscles from TG-ssTnI* and 96 ± 3% (n = 7) in muscles from TG-ssTnI hearts. Our results indicate that TnI isoform composition plays a crucial role in the determination of myocardial force sensitivity to acidosis.

AB - 1. Acidosis in cardiac muscle is associated with a decrease in developed force. We hypothesized that slow skeletal troponin I (ssTnI), which is expressed in neonatal hearts, is responsible for the observed decreased response to acidic conditions. To test this hypothesis directly, we used adult transgenic (TG) mice that express ssTnI in the heart. Cardiac TnI (cTnI) was completely replaced by ssTnI either with a FLAG epitope introduced into the N-terminus (TG-ssTnI*) or without the epitope (TG-ssTnI) in these mice. TG mice that express cTnI were also generated as a control TG line (TG-cTnI). Non-transgenic (NTG) littermates were used as controls. 2. We measured the force-calcium relationship in all four groups at pH 7.0 and pH 6.5 in detergent-extracted fibre bundles prepared from left ventricular papillary muscles. The force-calcium relationship was identical in fibre bundles from NTG and TG-cTnI mouse hearts, therefore NTG mice served as controls for TG-ssTnI* and TG-ssTnI mice. Compared to NTG controls, the force generated by fibre bundles from TG mice expressing ssTnI was more sensitive to Ca2+. The shift in EC50 (the concentration of Ca2+ at which half-maximal force is generated) caused by acidic pH was significantly smaller in fibre bundles isolated from TG hearts compared to those from NTG hearts. However, there was no difference in the force-calcium relationship between hearts from the TG-ssTnI* and TG-ssTnI groups. 3. We also isolated papillary muscles from the right ventricle of NTG and TG mouse hearts expressing ssTnI and measured isometric force at extracellular pH 7.33 and pH 6.75. At acidic pH, after an initial decline, twitch force recovered to 60 ± 3% (n = 7) in NTG papillary muscles, 98 ± 2% (n = 5) in muscles from TG-ssTnI* and 96 ± 3% (n = 7) in muscles from TG-ssTnI hearts. Our results indicate that TnI isoform composition plays a crucial role in the determination of myocardial force sensitivity to acidosis.

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Expression of slow skeletal troponin I in adult transgenic mouse heart muscle reduces the force decline observed during acidic conditions

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