Sep 1, 1989

Chronotropic and inotropic actions of amrinone, carbazeran and isobutylmethyl xanthine: role of phosphodiesterase inhibition

British Journal of Pharmacology
M Shahid, I W Rodger


1. The chronotropic and inotropic effects of amrinone, carbazeran and 3-isobutyl-1-methyl xanthine (IBMX) were examined in isolated preparations of papillary muscle and right atria from rabbit heart. The effects of the drugs on cardiac phosphodiesterase and cyclic nucleotide content were also examined. 2. Amrinone (2.4 x 10(-4)M-2 x 10(-3) M), carbazeran (9.1 x 10(-6) M-1.2 x 10(-3) M), and IBMX (1.8 x 10(-5) M-4.5 x 10(-4) M) produced concentration-dependent positive inotropic responses of papillary muscle preparations, the rank order of potency being carbazeran = IBMX greater than amrinone. Sub-threshold positive inotropic concentrations of all three compounds potentiated the positive inotropic effects of isoprenaline; leftward shifts in the concentration-effect curves were 5 fold (IBMX), 11 fold (amrinone) and 46 fold (carbazeran). 3. Amrinone and IBMX produced concentration-dependent positive chronotropic responses in isolated right atria and showed a similar rate selectivity to isoprenaline, but carbazeran elicited a decrease in beating frequency. None of these drugs potentiated the positive chronotropic effects of isoprenaline. 4. Concentrations of amrinone, carbazeran and IBMX that produced similar positive inotropic res...Continue Reading

Mentioned in this Paper

Myocardial Contraction
Phosphodiesterase Inhibitors
Cyclic GMP Measurement (Lab Test)
MORG1 protein, mouse
Phosphoric diester hydrolase

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