Elevated tissue levels of collagenase during dilation of uterine cervix in human parturition

Seven biopsy specimens from the cervix and 17 from the lower uterine segment were obtained in 24 women at term (37 to 42 weeks). Collagenase was extracted and assayed on telopeptide-free [³H]collagen; typical collagen cleavage products were found on sodium dodecyl sulfate-gel electrophoresis. There was no significant difference between collagenase levels in the cervix and in the lower uterine segment in women not in labor and with the cervix closed. Levels of active and latent collagenase in 11 such specimens were 0.14 ± 0.03 and 0.64 ± 0.90 U/gm wet weight, respectively (mean ± SEM; 1 U = 1 μg collagen digested per minute at 30° C). Thirteen women at term in active labor with cervical dilation of 4 to 8 cm exhibited a thirteenfold increase in mean collagenase activity in the lower uterine segment. Active and latent collagenase increased to 2.06 ± 0.92 and 8.64 ± 2.87 U/gm, respectively. This is the first direct evidence that interstitial collagenase increases markedly during cervical dilation in human parturition.