Relationship between maximum active stress and contractile protein contents in the chronically obstructed ureter

Maximum active stress and contractile protein contents of the dilated ureter were determined using the chronically obstructed rabbit ureter. Active length-tension curve was demonstrated for tissue strips obtained from normal and dilated ureters. In the normal ureter, maximum active stress of the strips was 10.4 +/- 2.04 X 10(4) dyne/cm.2 while the myosin and actin contents in the tissue were 6.05 +/- 0.44 and 15.46 +/- 1.96 mg./gm. tissue, respectively. Maximum active stress of the obstructed ureter varied from 5.1 X 10(4) to 19.0 X 10(4) dyne/cm.2 The amount of contractile protein in the obstructed ureter varied from 0.57 to 8.07 mg./gm. tissue for myosin and from 8.16 to 22.9 mg./gm. tissue for actin. For various degrees of ureteral dilatation, the active stress and contractile protein content showed similar changes. A significant correlation was demonstrated between maximum active stress and contractile protein content. The myosin amount was more closely correlated with maximum active stress, indicating that the content of myosin is a means of predicting contractility of the obstructed, dilated ureter.