LACK OF INFLUENCE OF CYCLOSPORINE-A ON LEVELS OF GINGIVAL PROCOLLAGENTYPE-I AND TYPE-III MESSENGER-RNAS IN RATS OF DIFFERENT AGES

Previous studies showed that gingival overgrowth following cyclosporin A (CsA) administration is not associated with an increase in intersti tial collagen. It also was shown that CsA causes a significant decreas e in collagen content within the gingival stroma. In order to determin e whether this decrease is caused by down-regulation of collagen mRNA, the procollagen mRNA level in gingiva of young and old rats was measu red and correlated with the ratio of interstitial collagen to DNA in t hese regions. Hybridization of P-32-labelled cDNA probes for procollag en types I and III with total RNA extracted from the molar gingiva sho wed that administration of CSA did not change the steady-state levels of mRNAs for both procollagens in the gingiva of either young or old r ats. The ratio of gingival interstitial collagen to DNA was significan tly reduced in the CsA-treated animals (4.2 +/- 0.85) relative to the controls (7.8 +/- 1.6). It is concluded that the reduction in intersti tial collagen following CsA treatment is not age-related, and is most probably caused by increased degradation rather by decreased biosynthe sis. (C) 1997 Elsevier Science Ltd.