Submitted to: Energy Metabolism of Farm Animals Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: September 15, 2000
Publication Date: January 1, 2001
Citation: Baldwin, R.L., Mcleod, K.R. 2001. Glucose oxidation by isolated steer duodenal enterocytes in vitro. Proceedings of the Energy Metabolism of Farm Animals. p. 217-220.
Interpretive Summary: Glucose is an important energy providing nutrient for animals. However, the intestines, where the glucose is absorbed, also use glucose which means the glucose is no longer useful to make milk and meat. The amount of glucose used by the intestines is currently being evaluated. These studies were conducted to determine how fast and at what concentrations cells of the intestine use glucose. Also, we sought to determine if a small peptide hormone, somatostatin, would change the rate of glucose use by the intestine. We used isolated cells from the intestine of steers and incubated them in flasks for 1 hour with different concentrations of glucose and somatostatin. We found that glucose was uses by the intestinal tissues of ruminants at lower concentrations than the rumen tissue. This means that the intestines use the glucose more readily than other tissues that make up the digestive tract in ruminants. We also demonstrated that somatostatin can change the maximal amount of glucose that is used by cells of the intestine. This is important because it demonstrates that glucose oxidation by intestinal cells can be altered by hormones in the animal. The estimates that we have developed will be helpful in the development of further experiments to clarify how much glucose is used by intestinal cells under different feeding conditions.
The objectives were to develop accurate estimates of the affinity for and the extent of glucose oxidation by ruminant enterocytes and to assess the effects of somatostatin-14 on these parameter estimates. Steers were fed a common forage diet ad libitum for at least 28-d prior to slaughter. At slaughter, duodenal tissue was collected and cells were isolated by collagenase digestion for analysis of glucose oxidation using 60 min incubations in vitro. Treatments included glucose (.001 to 30 mMoles/L) with somatostatin-14 (0 to 100 #M). Glucose (3 mMolar) oxidation to CO2 was linear over time for each animal, with R2 ranging from .65 to .92. Glucose dose response data were used to develop kinetic parameter estimates, Vmax and Kox, using the equation: Y = Vmax#(conc/ (Kox+conc)) in which Y= metabolite produced or substrate oxidized to CO2 (nMoles / 60 min) and conc = initial flask substrate concentration. Estimates of Vmax and Kox for glucose oxidation to CO2 are calculated to be 3.64 and 1.644, respectively. Both the Vmax and Kox estimates for glucose oxidation to CO2 were linearly decreased (P=0.06 and P=0.005, respectively) by somatostatin while lactate production by isolated entercytes was unaffected by somatostatin treatment. Somatostatin exerts direct effects on glucose metabolism in ruminant enterocytes.