Regional differences in water content, collagen content, and collagen degradation in the cervix of nonpregnant cows

The cow could be a suitable model for studies concerning functional changes of the cervix. However, as in many species, the bovine cervix becomes softer in texture during the follicular phase of the estrous cycle compared to the luteal phase. In the present study, we explored if changes in the collagen network take place that could be responsible for this phenomenon and if regional differences in water content, collagen content, and collagen degradation along the cross-sectional and longitudinal axes of the cervix were present. Two groups of nonpregnant animals with different progesterone status were studied. One group (n = 11) was under high progesterone influence, and the other group (n = 12) was under low progesterone influence. The water content was derived from the weight of the samples before and after lophilization. The collagen content and the ratio of collagenous to noncollagenous proteins (hydroxyproline:proline ratio) were determined by performing amino acid analysis on hydrolyzed samples using high-performance liquid chromatography. Collagen denaturation was quantified with a colorimetric assay by determining the amount of hydroxyproline released from samples treated with alpha-chymotrypsine. The water content of the superficial layer of the submucosa was always significantly (P < 0.01) higher than the water content of the deep layer in the vaginal, mid, and uterine segments, but this was unrelated to the progesterone status of the animals. No effect of the tissue layers or of the progesterone status of the animals on the collagen content was observed, but an effect of segment was noted. The collagen content (mug/mg dry wt) in the vaginal segment of the cervix was significantly higher than in the mid (P < 0.05) and the uterine (P < 0.01) segments. The hydroxyproline:proline ratio showed the same pattern as the collagen content. The percentage of collagen denaturation in the superficial layer was always significantly (P < 0.01) higher than that in the deep layer, but no effect of the progesterone status or of the segment along the longitudinal axis was seen. It is concluded that regional differences in collagen biochemistry are present in the cervix of nonpregnant cows, which may account for the difference in firmness of different parts along the circular or the longitudinal axis of the cervix. However, differences in texture of the cervix between the two groups of cows could not be explained by differences in the collagen content, percentage of collagen denaturation, or water content.