Sa. Burton et al., Evaluation of a glucose oxidase/peroxidase method for indirect measurementof glycogen content in oysters (Crassostrea virginica), J SHELLFISH, 19(2), 2000, pp. 841-844
A colorimetric method for indirect measurement of glycogen concentrations i
n tissue homogenates of eastern oysters (Crassostrea virginica) was evaluat
ed. This method uses a conversion of glycogen to glucose by amyloglucosidas
e. The procedure was optimized Fur extracting buffer pH (5.0) and amylogluc
osidase concentration (5 mg/mL). Coefficients of variation(n = 10) for oyst
er homogenates with mean glycogen concentrations of 84 and 242 mg/dL had wi
thin-run Values of 3.29 and 3.66%, and between-run results of 4.46 and 3.15
%, respectively. When mean glycogen concentrations of thawed oyster homogen
ates were compared with those of initial fresh homogenates, no significant
(P less than or equal to 0.05) differences were detected in samples thawed
after 1 h, 1 day, 1 wk, or 1 mo. Glycogen recovery percentages of 104.1, 10
3.7, and 104.5% were obtained with mixed solutions containing 111, 94, and
19 mg/dL glycogen, respectively. The lower limit of sensitivity for the pro
cedure was approximately 14 mL/dL. The assay was considered to be linear to
436 mg/dL. Lyophilized samples appeared to provide the most reliable deter
mination of glycogen concentrations per gram of tissue by avoiding variable
water content in oyster tissues. Initial laboratory ranges for tissue glyc
ogen based on wet (mean +/- 2 SD: 7-43 mg/g) and dry (mean +/- 2 SD: 19-145
mg/g) weights were determined with 49 second-year growth oysters obtained
during July 1998 (Covehead, Prince Edward Island, Canada). It was concluded
that the colorimetric assay offered a reliable indication of tissue concen
trations of glycogen in eastern oysters (C. virginica).