[Mechanism of action of AR-L 115 BS compared to caffeine]

The influence of 2-[(2-methoxy-4-methylsulfinyl)phenyl]-1H-imidazo[4,5-b]pyridine (AR-L 115 BS) and caffeine on Ca++-ATPase activity, Ca++-uptake and Ca++-release (efflux greater than influx:release) of the vesicles of sarcoplasmic reticulum of pig heart was investigated. In contrast to caffeine, 1 mmol/l AR-L 115 BS produced partial inhibition of Ca++-uptake of the vesicle while Ca++-release was only slightly affected. It was not possible to determine the effect of high concentrations of AR-L 115 BS and caffeine on the Ca++-ATPase activity because these substances showed a marked interference with the reagents of the reaction mixture.