[Sequential changes in maximum active stress, contractile proteins and collagen contents in obstructed ureters]

The sequential changes in maximum active stress, contractile proteins and collagen contents in the dilated ureter were determined in the rabbit ureters, which was partially obstructed for the intervals of 2 to 48 weeks. Maximum active stress and myosin content showed similar changes with the obstruction interval, i.e., both decreased first and then increased from week 2, and reached maximum at week 8, and after that, gradually decreased. Actin content did not show any significant changes. Collagen content showed almost the same changes as myosin content and maximum active stress by week 2. Then the collagen content increased rapidly from week 6 to week 10, and continued to increase gradually until 48 weeks after obstruction. A significant correlation was demonstrated between maximum active stress and myosin content while no significant correlation was found between maximum active stress and actin content. The maximum active stress decreased as the collagen content increased after week 8. Thus, there was a significant, negative correlation between them. Finally, the ratio of myosin content to collagen content (myosin/collagen) was related to maximum active stress. This ratio was more closely correlated with maximum active stress, indicating that myosin-collagen ratio is a good means of predicting contractility of the obstructed ureter.