Milrinone effects in the isolated immature rabbit heart.
Milrinone, a new positive inotropic agent, was evaluated and compared to isoproterenol in an immature isolated isovolumic rabbit heart model. Three age groups were studied: newborns (0-6 days), juveniles (4-6 weeks old) and adults (5-7 months old). Heart rate did not change significantly with milrinone or isoproterenol in adults or juveniles, but increased in newborns from 144 +/- 1 to 162 +/- (SEM) 6 beats/min at peak milrinone effect. Milrinone had a greater effect on the contractility (maximum positive dP/dt) of the mature hearts, with newborns increasing to 134 +/- 6% of baseline, juveniles to 154 +/- 8% and adults to 216 +/- 15%. Results were similar for isoproterenol, although the positive inotropic effect occurred over a wider dosage range for this drug. No additive effects of the two drugs were noted. We conclude, that although milrinone is a positive inotropic drug in all age groups studied, the response of the newborn heart is quantitatively much weaker than that of the adult.
Parrish
M D
MD
Department of Pediatrics, University of Texas Health Science Center, Dallas.
Brannon
T S
TS
Payne
A
A
Ayres
N
N
Fixler
D E
DE
D000375:Aging / Q000502:physiology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002316:Cardiotonic Agents / Q000494:pharmacology*; D006321:Heart / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D020105:Milrinone; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000378:metabolism; D009929:Organ Size; D010101:Oxygen Consumption / Q000187:drug effects; D011728:Pyridones / Q000494:pharmacology*; D011817:Rabbits
D002316:Cardiotonic Agents; D011728:Pyridones; D020105:Milrinone; D007545:Isoproterenol