Collagen studies in newborn rats with incomplete ureteric obstruction were performed to describe and quantify changes in
collagen deposition resulting from urinary tract obstruction at an early developmental age. Incomplete ureteric obstruction was created in three-day-old rats by placing the left ureter in a tunnel formed by the psoas muscle, and
sham-operated controls underwent a
laparotomy. The rats were sacrificed
at 10, 17, 24 or 31 days.
Collagen types I, III, IV, and V were localized by indirect immunofluorescence microscopy, the total
collagen content of the kidney was quantitated using
hydroxyproline analysis, and
collagen types I and III were quantitated using
cyanogen bromide (CNBr)
peptide analysis. Increased immunofluorescent staining for all of the
collagens was found in the diffusely widened medullary interstitium of the obstructed kidney, and more focally in the cortical interstitium.
Collagen types I, III and V, but not
collagen type IV, were also found in bands in the interstitium at the junction of the cortex with the medulla. Increased staining for
collagen type IV was found in thickened and tortuous tubular basement membranes (TBM) of the obstructed kidneys. The total
collagen content of the obstructed kidney was significantly increased compared to the amounts in both the contralateral kidneys and in the kidneys from
sham-operated controls at 24 and 31 days of age (P < 0.01 in each case, Wilcoxon matched pairs rank sum test and Mann Whitney U-test, respectively). The amount of
collagen in the kidneys correlated with the degree of
hydronephrosis (Spearman correlation test, r = 0.78, P < 0.02). CNBr
peptide analysis demonstrated that over 50% of the
collagen in the normal neonatal rat kidney was
collagen type I and approximately 25% was
collagen type III. In the obstructed kidneys most of the
collagen was also
collagen type I and
collagen type III, although the proportion of total
collagen comprised by these
collagen types was decreased compared with the controls. The amount of
collagen type III in the contralateral kidneys was reduced compared to that in the controls. Thus, the neonatal renal response to obstruction resulted in increased amounts of a range of
collagens in the interstitium and TBM, and the extent of this response was partially related to the degree of
hydronephrosis.