Effects of pindolol, befunolol and melanin treated with adrenergic beta-blocking agents on lysosomal enzymes in bovine ciliary body and iris in vitro.

We studied biochemically the effects of pindolol, befunolol and melanin treated with beta-blockers on lysosomal enzymes in the ammonium sulfate fraction of the bovine ciliary body and iris in vitro. Acid phosphatase, beta-D-glucuronidase and alpha-D-mannosidase were not inhibited by the beta-blockers. N-acetyl-beta-D-glucosaminidase and alpha-L-fucosidase activities were inhibited by pindolol and befunolol at high concentrations. After centrifugation of the enzyme fraction incubated with melanin, the enzyme activity in the supernatant decreased, possibly as a result of the affinity of lysosomal enzymes to melanin. When melanin was first treated with pindolol or befunolol, some lysosomal enzyme activities increased in the supernatant after removing the melanin, depending on the concentration of the beta-blocking agent. This increased activity may result from the loss of affinity of lysosomal enzymes to melanin caused by the beta-blocking agent.