Cardiac cell action potential duration is dependent upon induced changes in free Ca2+ activity during pH changes in vitro. J Electrocardiol 1986 Apr;19(2):143-54
Date
04/01/1986Pubmed ID
2423627DOI
10.1016/s0022-0736(86)80022-xScopus ID
2-s2.0-0022621762 (requires institutional sign-in at Scopus site) 2 CitationsAbstract
We examined how changes in solution pH alter myocardial cell action potentials (AP) with and without changes in free [Ca2+] caused by pH induced effects on calcium binding. Guinea pig ventricular tissue was isolated, superfused either with Krebs-Ringer (K-R) bicarbonate, phosphate buffered solution, or with Hepes buffered solution, and electrically paced during control (5% CO2 in O2), acidic (12% CO2), and alkalotic (0% CO2) conditions. Action potentials were recorded with intracellular microelectrodes. Extracellular free [Ca2+] was measured with a calcium ion selective electrode and total soluble calcium was measured by ultrafiltration and spectrophotometry. With a total [CaCl2] of 2.5 mM in the K-R solution, we found a free [Ca2+] of 2.14 mM at pH 7.44 (control), 2.48 mM at pH 6.97 and 1.60 mM at pH 8.19; total soluble calcium concentration was 2.00 mM at pH 8.19. In the Hepes solution, free [Ca2+] was only slightly altered (2.42 to 2.55 mM) within this pH range. Equivalent acidosis of either K-R or Hepes suffusate significantly, and similarly, prolonged the AP and its refractory period. Alkalosis of the Hepes suffusate shortened the AP; but equivalent alkalosis of the K-R suffusate prolonged the AP as did a reduction of [CaCl2] in Hepes suffusate from 3.0 to 1.5 mM at pH 7.43. Our study demonstrates that a paradoxical increase in APD occurs because free Ca2+ ion activity falls in K-R solution and overrides the effect of alkalosis alone to decrease APD.(ABSTRACT TRUNCATED AT 250 WORDS)
Author List
Stowe DF, Bosnjak ZJ, Kampine JPAuthor
David F. Stowe MD, PhD Professor in the Anesthesiology department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
Acid-Base EquilibriumAnimals
Calcium
Electrocardiography
Guinea Pigs
Heart Conduction System
Hydrogen-Ion Concentration
Ion Channels
Models, Cardiovascular
Ventricular Function