Inhibition of polyol formation in rat lens by verapamil

Accumulation of sorbitol and xylitol in rat lenses incubated in medium-199 with and without verapamil has been studied. This antihypertensive drug, known to attenuate hypertension by its calcium channel blocking effect, is also known to inhibit cataract formation in diabetes. The present studies have demonstrated that verapamil's effect against cataract could also be partially related to its aldose reductase inhibitory activity, in addition to the Ca++ channel blocking activity. The accumulation of sorbitol in the lenses incubated with high glucose in the presence of 400 microM verapamil was only 2.3 mmoles/Kg wet weight against 11.3 mmoles/Kg in its absence. The level of xylitol attained in the presence of 10 mM xylose was 25.7 +/- 2.4 mmoles/Kg. It decreased to 4.8 +/- 1.2 mmoles/Kg in presence of 400 microM verapamil. Hence, verapamil is significantly effective in inhibiting lens aldose reductase dependent polyol synthesis, an action simultaneous with its effect on calcium penetration.