English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Recovery of postischemic function may be limited by energy synthesis by mitochondria, energy transfer via the creatine kinase reaction, or energy utilization at myofibrils. To identify the limiting step, we defined the relations among oxygen consumption, creatine kinase reaction velocity and cardiac performance in myocardium reperfused following mild, moderate, and severe ischemia. Isolated isovolumic ferret hearts were perfused with Krebs-Henseleit buffer at 37 degrees C. After 30 minutes of control, hearts were made ischemic for 20, 40, or 60 minutes and reperfused for 40 minutes. During preischemia, cardiac performance (estimated as the rate-pressure product), was 14.8 x 10(3) mm Hg/min, oxygen consumption was 16.7 mumol/min/g dry weight, and creatine kinase reaction velocity measured by 31P-nuclear magnetic resonance saturation transfer was 12.7 mM/sec. For hearts reperfused after 20, 40, or 60 minutes of ischemia, rate-pressure product was 11.5, 6.5, and 1.1 x 10(3) mm Hg/min; oxygen consumption was 13.5, 14.2, and 6.9 mumol/min/g dry weight; and creatine kinase reaction velocity was 9.6, 5.0, and 2.0 mM/sec, respectively. Thus, with increasing severity of insult, creatine kinase reaction velocity decreased monotonically with performance (r = 0.99). Changes in creatine kinase reaction velocity were predicted from the creatine kinase rate equation (r = 0.99; predicted vs. measured velocity) and can therefore be explained by changes in substrate concentration. Oxygen consumption did not correlate with performance or creatine kinase velocity, consistent with abnormalities in mitochondrial energy production. In all cases, creatine kinase reaction velocity was an order of magnitude faster than the maximal rate of ATP synthesis estimated by oxygen consumption. We conclude that, in postischemic myocardium, creatine kinase reaction velocity decreases in proportion to performance, but high-energy phosphate transfer does not limit availability of high-energy phosphate for contraction.

Velocity of the creatine kinase reaction decreases in postischemic myocardium: a 31P-NMR magnetization transfer study of the isolated ferret heart.