Glucose turnover after a mixed meal in dogs: glucoregulation without change in arterial glycemia

Because the dog can respond to a mixed-meal challenge with little or no change in plasma glucose concentration, we used kinetic techniques to quantify the magnitude and duration of changes in glucoregulation. Glucose turnover was measured using [3-3H]glucose and [U-14C]glucose over two 19-h periods in healthy dogs, first during a fast (n = 6) and then throughout the postprandial state (n = 6) after a single mixed meal. Mean arterial glycemia remained constant in the fasted state (7.5 +/- 0.2 mM) and in the fed state (7.6 +/- 0.3 mM). Glucose appearance (Ra), however, increased slowly after the meal from 38 +/- 2 mg/min to a maximum of 79 +/- 8 mg/min after 6 h and stayed elevated until 12 h (P < 0.001). In parallel, glucose disappearance (Rd) rose from 35 +/- 3 to 83 +/- 7 mg/min, closely matching the corresponding Ra. Glucose recycling rose from 25 +/- 8% at baseline to a maximum of 53 +/- 15% (P < 0.05) at 14 h in fed dogs, whereas levels for fasted dogs stayed between 19 +/- 7% at 0 h and 27 +/- 12% at 6 h. Insulin levels rose significantly 30 min after the meal from 67 +/- 7 pM to a peak of 208 +/- 54 pM at 6 h but remained elevated for 12 h. We conclude that 1) the dog was able to maintain postprandial glucoregulation by very precise matching of Ra and Rd such as to maintain glycemia constant.(ABSTRACT TRUNCATED AT 250 WORDS)