Lusitropic changes induced by acid base alterations in cat papillary muscles

N. G. Perez, Alicia Mattiazzi, H. E. Cingolani

Research output: Contribution to journalArticlepeer-review

Abstract

The present work investigates the effects of acid-base alterations upon myocardial relaxation. Experiments were performed in cat papillary muscles contracting isometrically at constant frequency (0.2 Hz) and temperature (29°C). To induce intracellular alkalosis at constant pHo, 20 mM NH4CI were added to the perfusate. Alkalosis at variable pH0 was induced by switching from the control solution (5% CO2 -95% O2, pHo 7.40) to a solution identical to the control one, equilibrated with 3% CO2 -97% O2. Acidosis was induced by switching the control perfusate to a solution equilibrated with 12% CO2 -88% O2 in which pHo was either allowed to change or kept constant by manipulation of bicarbonate concentration. Alkalosis produced a negative lusitropic effect either when pHo was kept constant or when it was allowed to increase. For an increase in myocardial contractility of 30% half relaxation tme (T50) and time to peak tension (TTP) were prolonged 9.4 ± 5% and 5.4 ± 2% respectively at constant pHo and 6.8 ± 0.8 and 4.7 ± 1% respectively at variable pHo. It is suggested that this negative lusitropic effect of alkalosis can be attributed to an increase in myofilament sensitivity to calcium. Either at constant or at variable pHo acidosis decreased myocardial contractility by approximately 50% This decrease in contractility was accompanied by a positive lusitropic action only when pHo was allowed to decrease, or when acidosis at constant pHo was evoked in the presence of EIPA, a specific inhibitor of the Na+/H+ exchanger. The results indicate that the positive inotropic effect of a mild hypercapnic acidosis can be detected only if the degree of intracellular acidosis was enhanced after inhibition of the Na+/H+ exchanger. Under these conditions, a decrease in myofilament sensitivity to calcium can account for the positive lusitropic effect observed.

Original languageEnglish (US)
Pages (from-to)233-237
Number of pages5
JournalArchives of Physiology and Biochemistry
Volume101
Issue number3
DOIs
StatePublished - Jan 1 1993

Keywords

  • Acid-base changes
  • Cat
  • Myocardial relaxation
  • PH
  • Papillary muscles

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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