The changes in total tissue collagen content during a cycle of acute inflammation in young(1) and mature rats(2) have been described. In view of the recent interest in the soluble fractions of collagen(3) and the significance of the neutral solvent-soluble fractions in the biosynthesis of the collagen fibers (4), a reinvestigation of acute inflammation was carried out. In the present study, attention was centered on the relative proportions of the various collagen fractions in the tissue at different stages of a standard experimental acute inflammation.
Methods. Acute inflammation was induced in the antemolar region of the palates of Sprague-Dawley rats† by the method of Forscher and Stanley(5). The young group averaged 150 g body weight. The mature group were retired breeders (300 g average). Animals were sacrificed in groups of 10 by chloroform inhalation at selected time intervals after induction of the lesion. The palates were frozen in dry ice immediately after excision, crushed in the frozen state and taken through the extraction sequence as a pool of 10 samples. The soluble fractions were extracted by (1) distilled water (10 ml, 10 minutes), (2) 0.2N NaCl (10 ml, overnight at 4°C) and (3) 0.15 M citrate buffer pH 3.5 (10 ml, overnight at 4°C). After each extraction step, the mixture was centrifuged at 27,000 × g and the supernatant fluid was filtered through a Millipore filter, size GS, to remove fines. The entire soluble fraction at each step was freeze-dried and these residues as well as the final residue from the citrate extraction were hydrolyzed in 3N HCl at 105°C in sealed tubes overnight. Quadruplicate aliquots of the hydrolysates were analyzed for hydroxyproline by the method of Neuman and Logan(6).
The value for total hydroxyproline for a group was obtained by adding the values for the soluble fractions to the value for the insoluble residue.
Results. The total hydroxyproline content of the inflamed palates followed the pattern reported by Forscher and Cecil(2). In the soluble fractions, there was a marked difference between the changes in neutral solventsoluble fractions and citrate-soluble fraction, and a difference in response between young and mature animals.
