Effects of beta-2 agonist on metabolic regulation in the fetal lamb lung

D Warburton, L Parton, S Buckley, L Cosico and T Saluna

To study the effects of beta-2 agonist on metabolic regulation in fetal lamb lung, ritodrine hydrochloride, a preferential beta-2 agonist, was infused i.v. at a rate of 1.3 +/- 0.4 micrograms/kg/min (mean +/- S.D.) for 24 hr into six twin chronically catheterized fetal lambs starting between 0.86 and 0.91 gestation. Lung glycogen was depleted 56% in the ritodrine-infused twins and glycogen phosphorylase a activity was increased 1.8-fold whereas glycogen synthase activity remained unchanged. Cyclic AMP-dependent protein kinase activity increased 1.7- fold, calcium-calmodulin-dependent protein kinase (phosphorylase kinase) activity increased 1.4-fold and calcium-phospholipid-dependent protein kinase (protein kinase C) activity increased 1.6-fold. In addition, the maximal binding capacity of pulmonary beta receptors decreased 49% in the ritodrine-infused twins. However, lung cyclic AMP content was unchanged after 24 hr of ritodrine infusion. We conclude that beta-2 agonist activates protein kinases, depletes glycogen and reduces the binding capacity of beta receptors in the fetal lamb lung. We speculate that these adrenergic mechanisms are involved in regulating the effects of beta-2 agonist on fetal lung liquid and surfactant production.

Volume 242, Issue 2, pp. 389-393, 08/01/1987
Copyright © 1987 by American Society for Pharmacology and Experimental Therapeutics

This article has been cited by other articles:

				J. M. Bassett and M. E. Symonds beta 2-Agonist ritodrine, unlike natural catecholamines, activates thermogenesis prematurely in fetal sheep Am J Physiol Regulatory Integrative Comp Physiol, July 1, 1998; 275(1): R112 - R119. [Abstract] [Full Text] [PDF]