Effects of ryanodine and BAY K 8644 on membrane properties and conduction during simulated ischemia

T. Maruyama, W. E. Cascio, S. B. Knisley, J. Buchanan, L. S. Gettes

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Abstract

We studied the effect of 1.0 μM ryanodine and 0.1 μM BAY K 8644 (putative modulators of intracellular calcium) on the changes in action potential characteristics, cellular coupling, and longitudinal conduction induced by simulated ischemia (9.0 mM K, 6.5 pH, 0 glucose, 20 mmHg PO2) in superfused guinea pig papillary muscles. Simulated ischemia (SI) depolarized the resting membrane by 5 mV and caused a 28% decrease in action potential upstroke (V(max)), a 65% decrease in action potential duration at 90% (APD90), a 40% increase in internal longitudinal resistance (r(i)), and a 17% decrease in conduction velocity as compared with the 9-K Tyrode control solution. These changes were reversible and reproducible. The decrease in V(max) induced by SI was greater than that associated with a K+-induced change in resting membrane potential (RMP). Ryanodine lessened the SI-induced APD90 shortening by 26%, the decrease in V(max) by 42%, the increase in r(i) by 33%, and the decrease in conduction velocity by 21%. BAY K 8644 did not alter SI-induced APD90 shortening but augmented the decrease in V(max) by 23%, the increase in r(i) by 67%, and the decrease in conduction velocity by 59%. Neither ryanodine nor BAY K 8644 altered the SI-induced changes in RMP. Our results suggest that changes in intracellular calcium during SI not only influence cellular coupling but also contribute to the apparent non-RMP-dependent component of the change in V(max) and to the change in APD90 induced by SI.

Original languageEnglish
Pages (from-to)H2008-H2015
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume261
Issue number6 30-6
Publication statusPublished - Dec 1 1991
Externally publishedYes

Fingerprint

Ryanodine
Ischemia
Action Potentials
Membranes
Membrane Potentials
Calcium
Papillary Muscles
Guinea Pigs
Glucose

All Science Journal Classification (ASJC) codes

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

Cite this

Effects of ryanodine and BAY K 8644 on membrane properties and conduction during simulated ischemia. / Maruyama, T.; Cascio, W. E.; Knisley, S. B.; Buchanan, J.; Gettes, L. S.

In: American Journal of Physiology - Heart and Circulatory Physiology, Vol. 261, No. 6 30-6, 01.12.1991, p. H2008-H2015.

Research output: Contribution to journalArticle

Maruyama, T. ; Cascio, W. E. ; Knisley, S. B. ; Buchanan, J. ; Gettes, L. S. / Effects of ryanodine and BAY K 8644 on membrane properties and conduction during simulated ischemia. In: American Journal of Physiology - Heart and Circulatory Physiology. 1991 ; Vol. 261, No. 6 30-6. pp. H2008-H2015.
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