Using an in vitro culture system, we investigated the effects of five antiglaucoma drugs on growth and morphologic characteristics of bovine trabecular meshwork cells. Epinephrine hydrochloride (55-550 microM) and pilocarpine hydrochloride (0.8-16 mM), when added to the cultures for 3 days, inhibited trabecular cell growth in a dose-dependent manner. The lowest concentration at which the inhibitory effect was observed was 109 microM and 0.8 mM, respectively, for epinephrine and pilocarpine. Dipivefrin hydrochloride (26-260 microM), timolol maleate (116-1160 microM), and levobunolol hydrochloride (150-1500 microM) were also added to the cells for 3 days. These drugs caused a reduction in cell density, respectively, at concentrations higher than 103, 460, and 616 microM. Cell elongation was seen in cultures treated with epinephrine and dipivefrin, whereas levobunolol and timolol induced the cells to adopt a rounded appearance. Cells that had been exposed to pilocarpine were enlarged with numerous vacuoles. By scanning electron microscopic techniques, epinephrine, timolol, and levobunolol were found to retard the phagocytosis of latex beads by trabecular meshwork cells. Immunostaining with the use of antibodies to vimentin and actin revealed disorganization and condensation of cytoskeletal fibers in trabecular meshwork cells after treatment with epinephrine and dipivefrin. Little change was seen with comparable concentrations of a preservative, benzalkonium chloride, and a vehicle, Liquifilm tears. These results showed that antiglaucoma drugs, depending on their concentrations, may profoundly influence the growth and activity of trabecular meshwork cells.