Objective To investigate the role of calcineurin (CaN) in the lung fibroblast proliferation and collagen synthesis induced by basic fibroblast growth factor (bFGF).Methods We used Western blot and immunohistochemical methods for investigating the content and distribution of calcineurin in the lung tissue. Calcineurin activity in different tissues was measured using 32P-labelled substrate. In the primary culture of lung fibroblasts, 3H-thymidine (3H-TdR) and 3H-proline incorporation methods were used to study the effect of cyclosporin A (CsA), an inhibitor of calcineurin, on the lung fibroblast DMA and collagen synthesis stimulated by bFGF.Results We found that calcineurin was expressed in lung tissue and has phosphatase activity (7.1±2.0 pmol Pi/mg pr/min). CsA (10~(-8)-10~(-6) mol/L) inhibited lung fibroblast 3H-TdR incorporation induced by bFGF in a dose-dependent manner, with the inhibitory rates by 20% , 46% and 66% (P< 0.01). CsA (10~(-7) -10~(-6) mol/L) inhibited 3H-proline incorporation in lung Objective To investigate the role of calcineurin (CaN) in the lung fibroblast proliferation and collagen synthesis induced by basic fibroblast growth factor (bFGF). Methods We used Western blot and immunohistochemical methods for investigating the content and distribution of calcineurin in the lung tissue. Calcineurin activity in different tissues was measured using 32P-labeled substrates. In the primary culture of lung fibroblasts, 3H-thymidine (3H-TdR) and 3H-proline incorporation methods were used to study the effect of cyclosporin A (CsA), an inhibitor of Results showed that calcineurin was expressed in lung tissue and has phosphatase activity (7.1 ± 2.0 pmol Pi / mg pr / min) 10 ~ (-6) mol / L) inhibited lung fibroblast 3H-TdR incorporation induced by bFGF in a dose-dependent manner with the inhibitory rates of 20%, 46% and 66% (P <0.01) (-7) -10 ~ (-6) mol / L) 3H-proline inco rporation in lung