Increased collagenase activity is not detectable in cervical softening in the ewe

Cervical tissue from ewes at various stages of pregnancy was examined for evidence that collagenase is involved in the process of cervical softening. Collagenase activity was detected in medium after 2-3 days culture of ovine cervical explants, but there was no significant difference in total enzymic activity produced by explants from non-pregnant, early pregnant or late pregnant animals when expressed as units/mg wet weight of tissue over five days in culture. Oestradiol infusion into ewes prior to parturition did not alter the enzyme activity subsequently produced in explant culture. However, the DNA concentration, and hence the number of cells per unit volume, decreased significantly with length of pregnancy, this effect being due to expansion of cervical tissue which occurs late in pregnancy. Thus, if collagenase activity is expressed relative to DNA and hence cell number, there is evidence for increased production per cell in order to keep the tissue concentration constant. However, as the concentration of collagen in cervix remains constant during pregnancy, the ratio of collagenase activity to collagen is also constant. It is therefore concluded that there is no evidence of a role for increased collagenase activity in cervical softening in the ewe.