Yonsei Med J.  1988 Dec;29(4):341-349. 10.3349/ymj.1988.29.4.341.

Effect of Caffeine on Calcium Flux across the Sarcolemma of Guinea Pig Atrial Trabeculae during Contracture

• Suh CK
• Nam TS
• Kang BS

• KMID: 1729567
• DOI: http://doi.org/10.3349/ymj.1988.29.4.341

Abstract

The changes in extracellular calcium activities during contractures of guinea pig atrial trabecular muscles were measured with Ca2+-selective electrodes. When the tissue was superfused with Na+-free Tyrode solution extracellular Ca2+ activities were decreased and contractures were induced with some delay. When the contracture was relaxed with Na+-containing Tyrode solution, extracellular Ca2+ activities were increased transiently and recovered in a Na+-dependent manner. The magnitude of extracellular Ca2+ activity decreased was proportional to the maximum magnitude of contracture induced by Na+-free solution. Addition of caffeine (10 mM) to Na+-free solution induced transient contracture following slow development of contracture and an increase in extracellular Ca2+ activity. Removal of caffeine from Na+-free solution caused a slow relaxation of contracture and a decrease in extracellular Ca2+ activity. These results confirm that caffeine blocks Ca2+ uptake by the sarcoplasmic reticulum (SR) resulting in an increase in sarcoplasmic Ca2+ activity. Ca2+ activity in the extracellular space, the amount of Ca2+ transported into the cell(Ca2+ depletion in the extracellular space), and the magnitude of contracture are well correlated. Present experiments suggest that extracellular use of Ca2+-selective electrodes provides continuous and quantitative monitoring of Na+-dependent Ca2+ flux across the cardiac cell membrane.

Keyword

Contracture; Na+-Ca2+ exchange transport; caffeine; Ca2+-selective electrodes; guinea pig atrial trabeculae