Differential changes of prostanoid synthesis by the gastrointestinal tract, mesenteric vasculature and hepatic portal vein of diabetic rats: comparison between pair and ad libitum feeding.
The synthesis of the prostaglandins (PG) I2 (measured as 6-oxo-PGF1 alpha), E2, E2 alpha) and thromboxane (TX) A2 (measured as TXB2) by the mucosal and muscular portions of the stomach, duodenum, jejunum, ileum, mesenteric vessels, hepatic portal vein and two arteries (carotid and aorta) was investigated in long term streptozotocin-induced diabetes mellitus (DM; fed ad libitum and pair fed). In all regions of the gastrointestinal tract there were no changes in PG synthesis (per unit weight of tissue) in diabetic rats (pair fed or fed ad libitum) compared to controls. However, there were marked increases in PG synthesis (up to 3 fold) by the mesenteric vasculature and hepatic portal vein in diabetic animals fed ad libitum and in pair fed diabetic rats and decreases in the aorta and carotid artery. These data suggest that increases in PG synthesis by the splanchnic vasculature may constitute a specific adaptive response to DM. The similarity of the responses of pair fed rats to those of rats fed ad libitum indicates that DM and not hyperphagia is the likely determinant of these adaptive changes. Given that increased splanchnic blood flow enhances nutrient uptake (both known to occur in DM), the increase in splanchnic vascular PG synthesis, in particular of vasodilatory PGI2, may contribute to enhanced nutrient uptake.