Aug 19, 1975

Inotropic and electrophysiological actions of verapamil and D 600 in mammalian myocardium. II. Pattern of inotropic effects of the optical isomers

Naunyn-Schmiedeberg's Archives of Pharmacology
R BayerR Mannhold

Abstract

On isotonically contracting cat papillary muscles analysis, a comparison of the effects of the optical isomers of verapamil and D 600 and the racemic drugs was performed. 1. (-)-verapamil (0.2-3.0 mug/mo) and (-)-D-600 (0.1 mug/ml-3.0 mug/ml) leave the steady state contraction amplitudes nearly unchanged at 6/min, but produce a strong depression at 60/min. (-)-D 600 is about 8 times as effective as (-)-verapamil. The (+)-isomers exert only a moderate negative inotropic effect (particularly at low frequencies). 2. Increase of [Ca2+]O does not restitute the normal amplitude-frequency relationship during exposure to either the (-)-isomers or the (+)-isomers. 3. The (-)-isomers lead to typical biphasic staircases after step changes of frequency. A fast negative staircase occurs first followed by a rather slowly developing positive staircase. In contrast, the (+)-isomers have little influence on the usual staircase pattern. 4. The strength-interval relationship for single test contractions elicited after frequent conditioning stimulation indicated that the (-)-isomers probably slow the restitution of intracellular Ca-reavailability. The (+)-isomers have no such effects. 5. The effects produced by the (+/-)-compounds correspond quali...Continue Reading

Mentioned in this Paper

Myocardial Contraction
Molecular Stereochemistry
Depression, Chemical
Calcium
Myocardium
Dexverapamil
Optical Rotation
Electric Stimulation Technique
Felis catus

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