Effect of Different Doses of D‐Penicillamine and Combined Administration of D‐Penicillamine and Methylprednisolone on Collagen, Glycosaminoglycans, DNA and RNA of Granulation Tissue, Skin, Bone and Aorta in Rats

Abstract

D‐penicillamine (D‐pen) in doses of 20, 100 and 500 mg/kg/day or D‐pen 100 mg/kg/day plus methylprednisolone (MP) 2.0 mg/kg/day was administered daily for 42 days to rats implanted with viscose‐cellulose sponges. Operated, pairfed rats served as controls. D‐pen increased the DNA content of granulation tissue, but had no effect on the amount of tissue produced. In contrast, high dose D‐pen reduced the content of DNA and collagen in skin. A dose related inhibition of collagen crosslink formation occurred in all tissues, particularly in skin, as indicated by increased proportions of extractable collagen with increased α/β chain ratio and aldehyde content. Moreover, low doses of D‐pen increased the hydroxyproline/proline ratio of acid soluble skin collagen, presumably due to solubilization of type III collagen as demonstrated by SDS‐polyacrylamide gel electrophoresis in the presence of 3.6 M urea. These changes were associated with increased skin fragility and edema plus excess elastin deposition in the aorta after high dose D‐pen treatment. Low dose D‐pen stimulated the 35S‐sulphate uptake into the sulphated glycosaminoglycans (GAGs) of granulation tissue without altering their relative amounts, whereas high dose D‐pen reduced the concentration of chondroitin‐4/6‐sulphate in skin. MP antagonized the solubilizing effect of D‐pen on collagen, probably by inhibition of the collagen synthesis. In addition, MP inhibited the cell proliferation and GAG metabolism. Food restriction reduced the DNA content of granulation tissue. The inhibitory effect of D‐pen on the formation of granuloma collagen crosslinks in the presence of unaltered rate of collagen biosynthesis may diminish the amount of fibrotic tissue due to increased degradability of crosslink deficient collagen. Simultaneous administration of MP may facilitate this effect by inhibiting the biosynthesis of collagen. However, long‐term D‐pen treatment seems to increase the susceptibility of normal tissues to mechanical injury.