Endothelin-1 in monolayer cultures of articular chondrocytes from young and old rats: regulation by growth factors and cytokines

The endothelin-1 (ET-1) concentrations were measured by RIA in the media of confluent monolayer cultures of rat articular chondrocyte (RAC) exposed to fetal calf serum (FCS) and several growth factors and cytokines. The cells were obtained from 1- and 18-month-old rats. First passage cells were star ved in Dulbecco's modified Eagle's medium (DMEM) containing 0.2% FCS serum for 24 h and then incubated for 48 h in the same fresh medium with each of the following factors: fetal calf serum (FCS), transforming growth factor-b eta (TGF-beta). platelet-derived growth factor (PDGF), epidermal growth fac tor (EGF), insulin like growth factor-1 (IGF-1), interleukin-1 beta (IL-1 b eta), tumor necrosis factor alpha (TNF-alpha), lipopolysaccharide (LPS), an d NO donor, sodium nitroprusside (SNP). The following was found: the cells from 18-month-old animals accumulated about twice as much ET-1 per mu g DNA under basal (low serum) and stimulated conditions as cells from young rats . All, but PDGF and SNP produced concentration-dependent rise in ET-1 level s. the most effective being 10% FCS, IL-1 beta, TNF-alpha, EGF, IGF-1 and L PS. TGF-beta caused the smallest stimulation and PDGF was ineffective or sl ightly inhibitory at high concentrations. SNP caused concentration-dependen t decrease of ET-1 concentrations. ET-1-specific mRNA was identified by RT- PCR in cells incubated with the above factors and its concentration paralle led that of the peptide. This suggests that ET-1 found in the culture media of RAC stems, at least in part, from the synthesis. Increased immunoreacti ve peptide concentration and mRNA expression with the age of the donor rat and its regulation by several growth factors and cytokines suggest the invo lvement of ET-1 in chondrocytes' physiology and possibly pathology. (C) 200 0 Elsevier Science Ireland Ltd. All rights reserved.