Collagen solubility and tensile properties of the rat uterine cervix in late pregnancy: effects of arachidonic acid and prostaglandin F 2 alpha.

The collagen concentration in rat uterine cervix was less on day 18 of pregnancy than in the non-pregnant animal but did not diminish further as pregnancy proceeded. The solubility of cervical collagen in warm acetic acid (0.5 mol/l) was increased on day 22 compared with days 19, 20 and 21 of pregnancy, and there was a positive correlation of increasing solubility with the tissue rate of creep (a measure of reducing stiffness of the cervix). Treatment of rats subcutaneously with arachidonic acid or prostaglandin F 2 alpha (PGF 2 alpha) on day 18 of pregnancy decreased the stiffness of the tissue when assessed on day 19 and this was accompanied by increased solubility in cold saline (0.45 mol/1), cold acetic acid and warm acetic acid and a reduction in collagen concentration. These results suggest that collagen properties rather than concentration are important in determining the stiffness of the rat uterine cervix at term and that exogenous PGF 2 alpha and arachidonic acid cause biochemical changes in collagen structure unlike those seen at term in untreated animals.