The ability of white sturgeon to utilize different carbohydrates was studied by using a technique combining esophageal intubation, dorsal aorta cannulation, and urinary catheterization. Seven groups of five fish each were intubated with 1 g kg(-1) body weight of gelatin (sham), glucose, maltose, corn dextrin, potato dextrin, raw corn starch, or raw potato starch 48 h post-operation. The observed plasma glucose concentrations peaked at 6 h post-intubation of different carbohydrates and was the highest (10.2 +/- 0.5 mmol l(-1), mean +/- SEM, n = 5) in the glucose group. The glycemic index, which was measured for the first time in fish, was higher (P < 0.05) in the glucose group than in all other groups except for the maltose group. Urinary glucose excretion accounted for less than 1% of the total intubated dosage and it was significantly higher in the glucose group (5.16 +/- 1.25 mg kg(-1) 24 h(-1)) than in the sham (0.41 +/- 0.32 mg kg(-1) 24 h(-1)) and potato starch groups (0.31 +/- 0.23 mg kg(-1) 24 h(-1)). The first order kinetic function showed that complex carbohydrates delayed plasma glucose concentrations peak time and prolonged glucose efflux but did not affect glucose influx rate. The higher glucose efflux rate helped to alleviate the hyperglycemia in the glucose group. The present technique overcame some limitations of the previous oral challenge test and provided a more accurate description of carbohydrate utilization by white sturgeon. Glycemic index appeared to be a sensitive index to complement apparent digestibility coefficient determination and growth trials in evaluating carbohydrate utilization by white sturgeon. (C) 2001 Elsevier Science B.V. All rights reserved.
