Pulmonary surfactant release in fetal rabbits as affected by terbutaline and aminophyllin

Abstract

Terbutaline; a beta₂-adrenergic agonist, and aminophyllin, a phosphodiesterase inhibitor, were given separately, or in combination, to rabbit fetuses on the 28th day of gestation. The possibility of these drugs causing a release of pulmonary surfactant was evaluated 3 h after i.m. injection directly to the fetus. Lung compliance was studied and lung lavage fluid assessed as regards content of total phospholipid phosphorus, lecithin/sphingomyelin(L/S) ratio, and surface activity. It was found that terbutaline, in a dose of 0.1 mg, had a significant (P<0.05) effect on each of the four parameters studied and, when given in a dose of 0.05 mg, significantly affected all except L/S ratio. Aminophyllin, in a dose of 10 mg, resulted in a 40 % mortality, but in the surviving fetuses the drug had no significant (P>0.05) effect on any of the four parameters. When 5 mg aminophyllin was given together with 0.05 mg terbutaline, the effect could beattributed to terbutaline.

Key Words:

• lecithin/sphingomyelin
• Phospholipids
• respiratory distress syndrome
• pulmonary surfactant