Negative inotropic effects of XXXX in the neonatal piglet heart.

@entity1 @entity1707 @entity712 @entity301 @entity26 @entity2507 @entity11073
Cardiac mechanical function and @entity301 ( @entity301 ) were measured in isovolumically beating hearts from neonatal piglets 0.5 to 12 days of age. The hearts were perfused retrogradely at 70 cm @entity2507 with a recirculating modified Krebs-Henseleit solution containing washed adult @entity1707 red cells (hematocrit, 25%). They were electrically paced (180 beats/min), and left ventricular developed pressure (delta P), maximum rate of rise of pressure (dP/dt), @entity301 , and myocardial @entity26 consumption were measured. These parameters were found to remain stable for at least 60 minutes. In one group, a single dose of @entity11073 was added to the perfusate to yield a concentration of 50 micrograms/ml. Within 5 minutes delta P decreased from 104.0 +/- 7.1 to 65.3 +/- 8.6 mm Hg (p less than 0.001), and dP/dt fell from 1,160 +/- 96 to 658 +/- 78 mm Hg/sec (p less than 0.001). In a second group, successive doses of @entity11073 were added to yield concentrations ranging from 5 to 50 micrograms/ml. There was a progressive decrease in delta P and dP/dt to 66.5 +/- 4.2% and 57.6 +/- 4.8% of initial values, respectively. @entity301 increased progressively from 3.2 +/- 0.2 to 6.8 +/- 0.5 ml/min/g. In 3 experiments, @entity11073 was washed out after achieving the maximum concentration. Depressed mechanical function reversed and delta P and dP/dt returned to control values in each heart. Additionally, @entity301 decreased from 7.6 +/- 0.3 to 5.0 +/- 0.2 ml/min/g. It is concluded that @entity11073 has concentration-dependent negative inotropic actions in the neonatal piglet heart. Hence, the drug may not be useful in treating @entity712 in the @entity1 neonate.
