EFFECT OF AN ALDOSE REDUCTASE INHIBITOR, SNK-860, ON DEFICITS IN THE ELECTRORETINOGRAM OF DIABETIC RATS

To determine the effect of an aldose reductase inhibitor, SNK-860, on the worsening of the electroretinogram (ERG) during a diabetic state, rats with streptozotocin-induced diabetes were administered SNK-860 (1 or 4 mg kg(-1) orally) daily for 4 weeks. The effectiveness of SNK-860 in prolonging the peak latencies of oscillatory potentials in the b-wave of the electroretinogram of diabetic rats varied between these different waveform components (designated O-1, O-2 and O-3). SNK-860 (4 mg kg(-1) day(-1)) either completely or partially prevented the prolonged peak latencies at O-1 and Sigma(O-1 + O-2 + O-3). The drug failed to shorten the latency of the O-2 and O-3 components, and produced only a modest reduction in retinal levels of sorbitol and fructose, with no increase in myo-inositol. There was a significant correlation between the state of the ERG (components O-1 and Sigma(O-1 + O-2 + O-3)) and the retinal levels of sorbitol and fructose (P < 0.01), but not of myo-inositol. It is concluded that a better understanding of the mechanism by which SNK-860 acts may provide new insight into the pathogenesis of hyperglycaemic retinal dysfunction and help to establish effective therapy for diabetic retinopathy.