Effects of some Oral Hypoglycemic Drugs on Erythrocyte NADPH Methaemoglobin Reductase (E.C. 1.6.4.4) Activity of Albino Rats (Rattus rattus)

The invivo effects of three oral hypoglycaemic drugs viz., daonil (a glIbenclamide), diabenese (a sulphonylurea) and glucophage (a metformin) on erythrocyte nicotinamide-adenine dinucleotide phosphate hydrogen (NADPH) methaemoglobin reductase activity of Wister albino rats (Rattus rattus) were monitored at drug concentrations of 0.00, 0.01, 0.02 and 0.03mg/200g body weight. The effects of the drugs were monitored for fourteen days at intervals of 1, 2 , 6 and 14 day(s) followed by administration of each drug. Three rats were used per each drug concentration per time interval (days). NADPH activity was measured at pH 8.0 and at 37°C. Glucophage activated NADPH methaemoglobin reductase activity in a concentration dependent manner with optimal activity obtained at a concentration of 0.03mg/200g body weight and on the sixth day of drug administration. For instance, at drug concentrations of 0.00, 0.01, 0.02 and 0.03mg/200g body weight and at 6th day of administration, NADPH activity (IU/L) of 1.56 ± 0.04, 5.33+ 0.20, 7.45 ± 0.53 and 12.49 ± 0.62 were obtained for glucophage . The increase in enzyme activity following drug administration was progressive with time duration (in days). Maximum effect was obtained on the sixth day, which declines on the 14th day. At the same concentrations, the activities of NADPH methaemoglobin reductase for daonil were: 1.56 ± 0.03, 0.92 ± 0.09, 0.94 ± 0.11, 1.17 ± 0.01 respectively. Thus, there was an inhibitory effect when daonil was administered (P<0.05) while for diabenese there was no significant effect at P<0.05. Thus, only glucophage displayed a significant increase in activity (P<0.05). The implications of these findings to the functional integrity of erythrocytes are discussed in this work.