THE INOTROPIC EFFECT OF PROSTAGLANDIN (PG)E1AND PGD2IN THE NEWBORN RABBIT HEART

The purpose of this study was to determine the effects of PGE1and PGD2on mechanical function in the developing heart. The study was performed in the isolated, arterially perfused heart preparation of the newborn (NB) (N=34) and adult (A) (n=27) rabbits. Parameters of mechanical function [developed tension, maximal rate of contraction (+dT/dt), and relaxation (-dT/dt), and half relaxation time (1/2RT)] were recorded continuously. Positive inotropic effect was observed after PGE1or PGD2infusion in both NB and A. The effects of these drugs on +dT/dt (% of control) were:In NB, the relaxation parameters (1/2 RT and the ratio of +dT/dt to -dT/dt) decreased to 80% of control after PGE1infusion but not after PGD2infusion. In A, relaxation parameters were not different from control. These data indicate that 1) the positive inotropic effects of PGE1and PGD2in NB are greater than in A, and 2) PGE1, not PGD2enhances myocardial relaxation only in the NB.