Enhancement of Ca(2+) transients and contraction of single ventricular myocytes of rats by 5-(N,N-dimethyl) amiloride.

Abstract

The effects of 5-(N,N-dimethyl)amiloride (DMA) (a blocker of Na(+)/H(+) exchanger or Na(+)/Ca(2+) exchanger) on calcium transient and cell contraction in isolated ventricular myocytes in normal rats and rats with myocardial hypertrophy were examined using ion imaging system with a charge coupled digital camera (CCD camera). Loading myocytes with Fura-2, electrically triggered Ca(2+) transients and cell shortening were measured simultaneously. The results showed that 10 micromol/L DMA increased Ca(2+) transient and cell shortening from 209.60+/-54.96 and 3.07+/-0.97 micrometer to 238.50+/-80.41 and 4.07+/-1.02 micrometer, respectively (P<0.05), which was completely abolished by application of KB-R7943, a specific reverse mode Na(+)/Ca(2+) exchanger blocker. After blocking L-type Ca(2+) channels by nicardipine, DMA also enhanced Ca(2+) transient and cell shortening. In rats with myocardial hypertrophy, DMA showed the common pharmacologic profile as in normal rats but more intense stimulating effects on Ca(2+) transient and cell contraction. The results suggest that DMA increase Ca(2+) transient and cell contraction via stimulating reverse mode Na(+)/ Ca(2+) exchange, and the stimulating effect is more pronounced in rats with myocardial hypertrophy than in normal ones.

• Authors: Xiang-Li Cui, Huan-Zhen Chen, Dong-Mei Wu, Bo-Wei Wu
• Journal: Sheng li xue bao : [Acta physiologica Sinica] (Sheng Li Xue Bao) Vol. 54 Issue 3 Pg. 219-24 (Jun 25 2002) ISSN: 0371-0874 [Print] China
• PMID: 12075468 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Sodium-Calcium Exchanger
• 5-dimethylamiloride
• Amiloride
• Calcium

Topics

• Amiloride (analogs & derivatives, pharmacology)
• Animals
• Calcium (metabolism)
• Cardiomyopathy, Hypertrophic (drug therapy)
• Heart Ventricles (cytology)
• Myocardial Contraction (drug effects)
• Myocytes, Cardiac (metabolism)
• Rats
• Rats, Wistar
• Sodium-Calcium Exchanger (antagonists & inhibitors, pharmacology)