Streptozotocin-induced diabetes and the rat periodontium: decreased relative collagen production.

This is the first study concerning the extent to which relative collagen production (RCP) in rat periodontal tissues is affected by diabetes. Determination of RCP, rather than individual production rates for collagen or for non-collagen protein, was deemed necessary because saturation of all proline pools in tissues of diabetics (and non-diabetic controls) was not achieved. Such non-saturation occurred despite the injection of a pool-expanding dose of proline (400-1150 mg/rat), non-saturation indicated by the lesser specific radioactivity (S.R.) of free-[3H]proline in tissues than that of the injected solution. RCP was decreased in five periodontal tissues (incisor and molar gingiva, incisor and molar periodontal ligament, antemolar palatal mucosa) and in skin. Diabetes-decreased RCP seems to result from decreased collagen synthesis and increased intracellular degradation, although some evidence is presented for increased extracellular degradation of recently secreted collagen.

The appearance of free hydroxyproline as the major product of degradation of newly synthesized collagen in cell culture.

Embryonic lung fibroblasts and rabbit vascular smooth muscle cells have the ability to degrade newly synthesized collagen. Analysis of 24-h pulse media from cultures given [14C]proline demonstrates that greater than 90% of the degraded collagen is represented by free hydroxyproline rather than the peptide-bound imino acid. The addition of cycloheximide or alpha-alpha-dipyridyl to the culture medium during the pulse period severely diminished the formation of the free hydroxyproline demonstrating its enzymatic and protein (collagen) origin. It is proposed that assessment of free hydroxyproline formation may allow us to distinguish between intracellular and extracellular collagen degradation.