Beta-Adrenergic Sensitivity of the Fetal and Neonatal Rat Heart: Development of Methods for Measuring Beta-Adrenergic Receptor Population and Ornithine Decarboxylase Activity

摘要

The study defined the normal ontogenic patterns of ODC and its responsiveness to direct beta-adrenergic stimulation, and provided a data base that will be used in future studies on alterations of cardiac development following prenatal insult. In the adult rat, beta-adrenergic stimulation of cardiac growth parallels ornithine decarboxylase (ODC) activation, and the ability of cardiac ODC to respond to sympathetic nervous system (SNS) stimulation is used as an indicator of the intactness of the sympathetic pathway to the heart. To determine the effect of prenatal drug exposure on the development and sympathetic innervation of the heart, it is necessary to define the normal postnatal alterations in basal ODC and its responsiveness to direct beta-adrenergic stimulation. ODC activity was measured in rat hearts on gestation day (GD) 20 through postnatal day (PND) 28 under saturating conditions of L-ornithine and pyridoxal-1-phosphate. Basal ODC activity fell from 3 nmol CO2/mg protein/hr at GD 20 to less than 0.5 nmol CO2/mg protein/hr at PND 18, rising again to nearly 1 nomol CO2/mg protein/hr at PND 22.