A: Treatment of mBECs kept in C-SFM with cyclosporine (5,000 ng/ml), but not tacrolimus (1,000 ng/ml) caused an increase of TGF-β mRNA production, as determined by a standard ribonuclease protection assay. If the mBECs were growth arrested by switching to simple serum-free medium (S-SFM) (see Materials and Methods) there was also an increase in TGF-β production. B: Densitometry tracing and comparison to GAPDH mRNA showed that TGF-β mRNA production is higher in the cyclosporine-treated than in the tacrolimus-treated cultures. The determinations were performed 24 hours after the addition of the drugs to the mBEC cultures kept in C-SFM. The results shown are representative of three separate experiments. C: Treatment of mBECs kept in C-SFM with cyclosporine (1,000 ng/ml), but not tacrolimus (1,000 ng/ml) for 48 hours caused an increase of TGF-β protein secretion into the culture supernatant, as determined by a standard enzyme-linked immunosorbent assay (*, P < 0.005).