Effect of Caffeine on Calcium Flux across the Sarcolemma of Guinea Pig Atrial Trabeculae during Contracture.
10.3349/ymj.1988.29.4.341
- Author:
Chang Kook SUH
1
;
Taick Sang NAM
;
Bok Soon KANG
Author Information
1. Department of Physiology, Yonsei University College of Medicine, Seoul, Korea.
- Publication Type:Original Article ; Research Support, Non-U.S. Gov't
- Keywords:
Contracture;
Na+-Ca2+ exchange transport;
caffeine;
Ca2+-selective electrodes;
guinea pig atrial trabeculae
- From:Yonsei Medical Journal
1988;29(4):341-349
- CountryRepublic of Korea
- Language:English
-
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.
