EVALUATION OF A GLUCOSE-OXIDASE PEROXIDASE METHOD FOR INDIRECT MEASUREMENT OF GLYCOGEN-CONTENT IN MARINE MUSSELS (MYTILUS-EDULIS)

A colorimetric method (glucose oxidase/peroxidase) for indirect measur ement of glycogen concentrations in tissue homogenates of marine musse ls (Mytilus edulis) was evaluated. This method uses a conversion of gl ycogen to glucose by amyloglucosidase. Varying the buffer pH (4.5, 5.0 ; 5.5) and the amyloglucosidase concentration (160, 80, 40, 20, 10, 5, 1, and 0.5 mg/mL) did not appreciably optimize glycogen concentration . Coefficients of variation (n = 10) for mussel homopenates with mean glycogen concentrations of 94 and 334 mg/dL had within-run values of 0 .75 and 0.96%, respectively. The between-run coefficients of variation (n = 10) for the same homogenates were 2.10 and 1.10%, respectively. When mean glycogen concentrations of thawed mussel homogenates were co mpared with those of initial fresh homogenates, a significantly (p les s than or equal to 0.05) lower glycogen concentration was seen in samp les thawed after 1 day, but not in samples thawed after 1 h, 1 wk, or 1 me. Glycogen recovery percentages of 99.3, 99.0, and 95.6% were obta ined with mixed solutions containing 103.8, 95.2, and 10.8 mg/dL glyco gen, respectively. The lower limit of sensitivity for the procedure wa s approximately 10 mg/dL. Because dilutions of a mussel homogenate wit h a high glycogen concentration (413.1 mg/dL) gave observed results wi thin 5% of expected results, the assay was considered to be linear to at least 413.1 mg/dL. Glycogen concentrations based on analysis of wet tissue and lyophilized samples from 20 mature mussels were compared, resulting in a significant (p less than or equal to 0.05) correlation coefficient of 0.52. An initial laboratory range (43-91 mg/g) for tiss ue glycogen based on wet weights (3.9-12.4 g) was determined with 20 m ature mussels during July from the Morell region, Prince Edward Island , Canada. It was concluded that the colorimetric assay offered a relia ble indication of tissue concentrations of glycogen in marine mussels (M. edulis).