Diabetes is accompanied by delayed wound healing and insufficient granulation tissue formation, possibly because of a defect in fibroblast function. We have previously shown that fibroblasts derived from chronic diabetic foot ulcers have lower proliferation compared with those from uninjured skin. The aim of this study was to investigate possible mechanisms explaining the impaired fibroblast proliferation observed in fibroblasts from non-insulin-dependent diabetes mellitus chronic wounds and normal fibroblasts cultured in high glucose. Fibroblasts from two groups of patients were studied: nondiabetic patients with chronic venous stasis ulcers and non-insulin-dependent diabetes mellitus patients with chronic diabetic wounds. Biopsies from both uninjured skin and wounds were taken from the same patients to serve as sources of fibroblasts. A fluorometric method was used to determine DNA content, and a spectrophotometric lactate oxidase method was used for lactate level analysis. We found a dose-dependent inhibition of normal fibroblast proliferation when adding conditioned media from non-insulin-dependent diabetes mellitus wound fibroblasts. The conditioned medium, from these cells showed elevated l-lactate levels, 6.3 +/- 0.7 mmol/L, compared with media derived from nondiabetic, 2.1 +/- 0.3 mmol/L (p < 0.01), and diabetic uninjured skin fibroblasts, 3.5 +/- 0.6 mmol/L, and from chronic nondiabetic wound fibroblasts 2.9 +/- 0.3 mmol/L. Addition of 6 mmol/L l-lactate to uninjured normal fibroblasts resulted in decreased DNA content (58 +/- 7%, p < 0.01). Previously we have shown that high glucose concentrations inhibit fibroblast proliferation and induce growth factor resistance. When increasing the amount of d-glucose in the media, l-lactate levels increased in all cell types. When the uninjured normal cells were treated with beta-hydroxybutyrate, the total DNA content decreased by 42 +/- 5% (p < 0.05), with no significant increase in the l-lactate levels. These observations indicate that l-lactate production may be of importance for fibroblast proliferation in vitro and may play a role in fibroblast proliferation in vivo.