Antiproliferative drugs and human ocular fibroblasts: colorimetric vs. cell counting assays

Utilizing a rapid colorimetric assay that relates cell number to cytoplasmic hexosaminidase activity, we conducted drug-induced cytotoxicity experiments on human ocular fibroblasts cultured from Tenon's capsule specimens. The effects of two different agents--dimethyl sulfoxide (DMSO) or mitomycin C--on the proliferation of human ocular fibroblasts were studied. Simultaneously the sensitivity of this technique was compared to electronic cell counting with a Coulter counter, a conventional means of quantifying proliferation. Known numbers of cells were exposed to varied concentrations of either DMSO or mitomycin C for 11 days. Cell attachment was quantified after 24 hours, and proliferation was quantified periodically thereafter over the remaining 10 days. Colorimetric data contained a similar or smaller amount of random error than corresponding Coulter values. Both assays identified statistically significant antiproliferative effects and inhibitory effects on cell attachment at higher drug doses; however, Coulter counting alone detected many additional significant effects among lower-dose DMSO and mitomycin treatment groups. Although the hexosaminidase assay displayed lower sensitivity than Coulter counting, it may still be useful to rapidly screen new compounds for strong antifibroblastic effects.