Faculty Collaboration Database

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

04/01/1986

Pubmed ID

2423627

DOI

10.1016/s0022-0736(86)80022-x

Scopus ID

2-s2.0-0022621762 (requires institutional sign-in at Scopus site)   2 Citations

Abstract

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 JP

Author

David F. Stowe MD, PhD Professor in the Anesthesiology department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Acid-Base Equilibrium
Animals
Calcium
Electrocardiography
Guinea Pigs
Heart Conduction System
Hydrogen-Ion Concentration
Ion Channels
Models, Cardiovascular
Ventricular Function