The relationship between intracellular [Ca²⁺] and Ca²⁺ wave characteristics in permeabilised cardiomyocytes from the rabbit

Loughrey, C.M. , MacEachern, K.E. , Neary, P. and Smith, G.L. (2002) The relationship between intracellular [Ca²⁺] and Ca²⁺ wave characteristics in permeabilised cardiomyocytes from the rabbit. Journal of Physiology, 543(3), pp. 859-870. (doi: 10.1113/jphysiol.2002.021519) (PMID:12231644)

Abstract

Spontaneous sarcoplasmic reticulum (SR) Ca²⁺ release and propagated intracellular Ca²⁺ waves are a consequence of cellular Ca²⁺ overload in cardiomyocytes. We examined the relationship between average intracellular [Ca²⁺] and Ca²⁺ wave characteristics. The amplitude, time course and propagation velocity of Ca²⁺ waves were measured using line-scan confocal imaging of beta-escin-permeabilised cardiomyocytes perfused with 10 muM Fluo-3 or Fluo-5F. Spontaneous Ca²⁺ waves were evident at cellular [Ca²⁺] > 200 nm. Peak [Ca²⁺] during a wave was 2.0-2.2 muM; the minimum [Ca²⁺] between waves was 120-160 nm; wave frequency was similar to0.1 Hz. Raising mean cellular [Ca²⁺] caused increases in all three parameters, particularly Ca²⁺ wave frequency. Increases in the rate of SR Ca²⁺ release and Ca²⁺ uptake were observed at higher cellular [Ca²⁺], indicating calcium-sensitive regulation of these processes. At extracellular [Ca²⁺] > 2 muM, the mean [Ca²⁺] inside the permeabilised cell did not increase above 2 muM. This extracellular-intracellular Ca²⁺ gradient could be maintained for periods of up to 5 min before the cardiomyocyte developed a sustained and irreversible hypercontraction. Inclusion of mitochondrial inhibitors (2 muM carbonyl cyanide m-chlorophenylhydrazone and 2 muM oligomycin) while perfusing with > 2 muM Ca²⁺ abolished the extracellular-intracellular Ca²⁺ gradient through the generation of Ca²⁺ waves with a higher peak [Ca²⁺] compared to control conditions. Under these conditions, cardiomyocytes rapidly (< 2 min) developed a sustained and irreversible contraction. These results suggest that mitochondrial Ca²⁺ uptake acts to delay an increase in [Ca²⁺] 1 by blunting the peak of the Ca²⁺ wave.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Smith, Professor Godfrey and Loughrey, Professor Christopher and MacEachern, Dr Karen
• Authors: Loughrey, C.M., MacEachern, K.E., Neary, P., and Smith, G.L.
• College/School: College of Medical Veterinary and Life Sciences > School of Cardiovascular & Metabolic Health; College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
• Journal Name: Journal of Physiology
• ISSN: 0022-3751
• ISSN (Online): 1469-7793
• Published Online: 22 July 2002