Cardiac troponin-I phosphorylation underlies myocardial contractile dysfunction induced by hypothermia rewarming

Torkjel Tveita, Grace M Arteaga, Young Soo Han, Gary C. Sieck

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

Rewarming the intact heart after a period of hypothermia is associated with reduced myocardial contractility, decreased Ca2+ sensitivity, and increased cardiac troponin-I (cTnI) phosphorylation. We hypothesized that hypothermia/rewarming (H/R) induces left ventricular (LV) contractile dysfunction due to phosphorylation of cTnI at Ser23/24. To test this hypothesis, the response of wild-type mice (n = 7) to H/R was compared with transgenic (TG) mice expressing slow skeletal TnI (TG-ssTnI; n = 7) that lacks the Ser23/24 phosphorylation sites. Hypothermia was induced by surface cooling and maintained at 23-25°C for 3 h. Subsequently, the animals were rewarmed to 37°C. LV systolic and diastolic function was assessed using a 1.4 F pressure-volume Millar catheter introduced via the right carotid artery. At baseline conditions, there were no significant differences in LV systolic function between wild-type and TG-ssTnI mice, whereas measurements of diastolic function [isovolumic relaxation constant (τ) and end-diastolic pressure-volume relationship (EDPVR)] were significantly (P < 0.05) reduced in TGssTnI animals. Immediately after rewarming, significant differences between groups were found in cardiac output (CO; wild-type 6.6 ± 0.7 vs. TG-ssTnI 8.8 ± 0.7 mL/min), stroke work (SW; wildtype 796 ± 112 vs. TG-ssTnI 1208 ± 67 mmHg/L), and the preload recruited stroke work (PRSW; wild-type 38.3 ± 4.9 vs. TG-ssTnI 68.8 ± 8.2 mmHg). However, EDPVR and τ returned to control levels within 1 h in both groups. We conclude that H/R-induced LV systolic dysfunction results from phosphorylation of cTnI at Ser23/24. NEW & NOTEWORTHY Rewarming following a period of accidental hypothermia leads to a form of acute cardiac failure (rewarming shock), which is in part due to reduced sensitivity to Ca2+ activation of myocardial contraction. The results of the present study support the hypothesis that rewarming shock is due to phosphorylation of cardiac troponin I.

Original languageEnglish (US)
Pages (from-to)H726-H731
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume317
Issue number4
DOIs
StatePublished - Jan 1 2019

Keywords

  • Hypothermia
  • Rewarming
  • Transgenic slow skeletal Tnl
  • Troponin I

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

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