Effects of Beta-2 Agonist on Metabolic Regulation in the Fetal

To study the effects of beta2 agonist on metabolic regulation in fetal Iamb lung, ntodnne hydrochloride, a preferential beta-2 agonist, was infused i.v. at a rate of 1.3 ± 0.4 g/kg/min (mean ± S.D.) for 24 hr into six twin chronically catheterized fetal lambs starting between 0.86 and 0.91 gestation. Lung gtycogen was depleted 56 % in the ritodrine-infused twins and glycogen phos-phorylase a activity was increased 1.8-fold whereas glycogen synthase activity remained unchanged. Cydic AMP-dependent protein kinase activity increased 1.7-fold, calcium-calmodulin-dependent protein kinase (phosphorylase kinase) activity in-creased 1.4-fold and caldum-phospholipid-dependent protein ki-nase (protein kinase C) activity increased 1.6-fold. In addition, the maximal binding capacity of pulmonary beta receptors de-creased 49 % in the ritodnneinfused twins. However, lung cydi