EFFECTS OF ADRENERGIC AGENTS AND PHOSPHODIESTERASE INHIBITORS ON OUTFLOW FACILITY AND CELL-SHAPE OF BOVINE TRABECULAR MESHWORK

Changes in the outflow facility of perfused calf eyes and in the shape of cells in cultured trabecular meshwork (TM) have been studied, foll owing exposure to adrenergic agents and phosphodiesterase inhibitors ( PDE). Dobutamine caused confluent TM cells to change their usual polyg onal shape to a characteristic stellate shape. Salbutamol had no effec t, but PDE: inhibitors, isobutylmethylxanthine (IBMX), theophylline, a nd caffeine were very effective in producing this shape change. Epinep hrine, isoproterenol, dobutamine, and salbutamol did not increase the outflow facility, either at 22 degrees C or 36 degrees C, while theoph ylline, caffeine, and IBMX did increase it in a dose-dependent manner. On the other hand, the high concentrations of beta-adrenergic agents required to produce even a small change in outflow facility and cell s hape argue against the involvement of adrenergic-receptor mediation an d may suggest another mechanism; on the other, the enhancement of epin ephrine effects by PDE inhibitors and the similar effect produced by c yclic adenosine 3',5'-cyclic phosphate (cAMP) and purines suggest that changes in the cell shape are produced by beta-receptor activation. T he beta-adrenergic agents were not effective in changing outflow facil ity, but the PDE inhibitors were remarkably effective both in changing the shape and in increasing facility. (C) 1997 Japanese Ophthalmologi cal Society.