Effects of meal size on postprandial responses in juvenile Burmese pythons (Python molurus).

Pythons were reported previously to exhibit large changes in intestinal mass and transporter activities on consuming meals equal to 25% of the snake's body mass. This paper examines how those and other adaptive responses to feeding vary with meal size (5, 25, or 65% of body mass). Larger meals took longer to pass through the stomach and small intestine. After ingestion of a meal, O2 consumption rates rose to up to 32 times fasting levels and remained significantly elevated for up to 13 days. This specific dynamic action equaled 29-36% of ingested energy. After 25 and 65% size meals, plasma Cl- significantly dropped, whereas plasma CO2, glucose, creatinine, and urea nitrogen increased as much as a factor of 2.3-4.2. Within 1 day the intestinal mucosal mass more than doubled, and masses of the intestinal serosa, liver, stomach, pancreas, and kidneys also increased. Intestinal uptake rates of amino acids and of D-glucose increased by up to 43 times fasting levels, whereas uptake capacities increased by up to 59 times fasting levels. Magnitudes of many of these responses (O2 consumption rate, kidney hypertrophy, and D-glucose and L-lysine uptake) increased with meal size up to the largest meals studied; other responses (Na+-independent L-leucine uptake, plasma Cl-, and organ masses) plateaued at meals equal to 25% of the snake's body mass; and still other responses (nutrient uptake at day 1, passive glucose uptake, and plasma protein and alkaline phosphatase) were all-or-nothing, being independent of meal size between 5 and 65% of body mass. Pythons undergo a wide array of postprandial responses, many of which differ in their sensitivity to meal size.