An experimental study on the effects of elastase, bleomycin and infection on the growth and tensile strength of elastic tissue in rabbit fetal membranes.

The effects of bleomycin, elastase and infection on the tensile strength of rabbit fetal membranes and the structure of the elastic tissue of rabbit amnion were studied. The experimental subjects were rabbits to which bleomycin (total dose, 20 mg) or elastase (total dose, 60 mg) was administered from 18 days of pregnancy. In addition to the fetal membranes from these treated animals, fetal membranes with amniotic infection induced by injection of Escherichia coli into the amniotic fluid (AF) of rabbits at 22 or 23 days of pregnancy were examined, and those from rabbits administered physiological saline solution were used as controls. The results obtained were as follows. Determination of tensile strength of the fetal membranes revealed that the infected membranes had minimum rupture pressure (18.67 +/- 6.30 mm Hg), followed by the elastase administration group (46.67 +/- 3.51 mm Hg). The value in the bleomycin administration group (99.67 +/- 12.89 mm Hg) was significantly higher than that in the control group (61.80 +/- 6.30 mm Hg). Histological changes in the fibroblast layer of these fetal membranes included elastic fibrosis due to excessive collagen production, which was mostly manifested as fibrosis densa, in the bleomycin administration group. In the elastase administration group, the elastic fibers were eliminated or became minute, as in the infection groups. The above results showed the adverse effects of elastase and bleomycin and the destructive effect of infection on the growth and properties of elastic tissue in the amnion, suggesting their pathophysiological importance.