Quinidine enhances intracellular Ca 2+ accumulation during rapid stimulation

• Published in: General pharmacology Vol. 26; no. 5; pp. 971 - 976
• Main Authors: Hasegawa, Junichi, Tsuboi, Mariko, Narasaki, Kohshi, Hirai, Shozo, Nawada, Takahiro, Kotake, Hiroshi, Mashiba, Hiroto
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 1995
• Subjects: anti-arrhythmic effect; fura-2; Intracellular Ca 2+i calcium staircase; quinidine; quinidine; anti-arrhythmic effect; fura-2; Intracellular Ca 2+ i calcium staircase
• ISSN: 0306-3623; 1879-0011
• DOI: 10.1016/0306-3623(94)00297-Z

1. 1. The quinidine-induced modification of intracellular Ca 2+ concentration ([Ca 2+] i) was studied in guinea-pig myocardium using fura-2. Quinidine reduced the systolic fluorescence signal level for [Ca 2+] i and enhanced the end-diastolic signal level during a stimulation train. 2. 2. The diastolic decay of [Ca 2+] i fitted 2 exponential curves. Quinidine distorted the stimulation frequency-dependent acceleration of rapid [Ca 2+] i decay, and prolonged the mean time constant of rapid decay after 2 Hz stimulation, from 154.4 to 205.3 msec (20 μM), and to 259.7 msec (60 μM quinidine). The time constant of slow recovery from [Ca 2+] i accumulation after the stimulation train was not affected by stimulation frequency, or by quinidine, or caffeine. 3. 3. These results suggest that quinidine modulates [Ca 2+] i via a balance between the slowing of rapid [Ca 2+] i decay and the reduction of the systolic [Ca 2+] i. This effect may contribute to the anti-arrhythmic and pro-arrhythmic effects exerted by quinidine in some conditions.