Evaluation of LDH and G6-PDH Activities in Auditory Relay Centers of Streptozotocin-induced Diabetic Wistar Rats

This study was designed to assess the direct effects of chronic hyperglycemia on the hearing pathway with reference to the auditory relay nuclei—the medial geniculate body (MGB) and inferior colliculus (IC)—based on the biochemical assay of carbohydrate metabolic pathways using marker enzymes as reference points. A total of 39 healthy adult Wistar rats (of both sexes) weighing 200- 220g were used in this study. Twenty-four of them were rendered diabetic by a single STZ intraperitoneal injection of 70 mg/kg body weight; fifteen were used as control. Activities of lactate dehydrogenase (LOH) for the glycolytic pathway and glucose-6-phosphate dehydrogenase (G6-PDH) for the pentose phosphate pathway were assessed at post-induction periods P4, P7 and P10 (in weeks). The activities of the enzymes decreased (P<0.05) through the periods of assessment as revealed by the biochemical assay results (Tables 2 & 3). The study offers fresh evidence that STZ-induced diabetes mellitus can cause a derangement in the pathways of carbohydrate metabolism in the medial geniculate body and inferior colliculus and may be implicated as one of the factors responsible for the mechanism of bearing impairment experienced in diabetic conditions.

Key Words: streptozotocin (STZ), diabetes mellitus (DM),   medial  geniculate  body (MGB), inferior colliculus (IC), lactate dehydrogenase (LDII),  succinate dehydrogenase (SDII), glucose-6-phosphate dehydrogenase (G6-PDH)