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 to 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 less then 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 greater than 0.05) effect on any of the four parameters. When 5 mg aminophyllin was given together with 0.05 mg terbutaline, the effect could be attributed to terbutaline.
Prospective studies of pregnant women were performed to compare individual variations in the plasma concentration of sex hormone binding globulin (SHBG) and pregnancy zone protein (PZP) during pregnancy, and to elucidate the degree of co-variation between these oestrogen sensitive proteins during gestation. The plasma concentration of SHBG manifested continuous increase reaching a 12-fold peak at delivery. The increase of the protease inhibitor PZP paralleled that of SHBG reaching a peak with a 25-fold increase by the beginning of the third trimester. Then it started to decline, while that of SHBG continued to increase. The synthesis of the protease inhibitor may also continue to increase during late gestation but its elimination from the circulation may be accelerated when the syncytiotrophoblastic area in contact with the maternal blood approaches its maximum. The unusually wide individual variation of PZP concentrations in non-pregnant women was confirmed. However, the individual levels increased proportionally during the progress of pregnancy, and we may speak of low, medium and high reactors for PZP. One initial conclusion to be drawn from the present findings is that the value of the plasma PZP concentration can only be interpreted from a pathophysiologic point of view if the patient's baseline level is known.
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