SPLANCHNIC RETENTION OF INTRADUODENAL AND INTRAJEJUNAL GLUCOSE IN HEALTHY-ADULTS

Estimates of the spanchnic retention and appearance in the systemic ci rculation of orally administered glucose vary among laboratories even after recently identified sources of error have been accounted for [Li vesey, G., P. D. G. Wilson, J. R. Dainty J. C. Brown, R. M. Faulks, M. A. Roe, T. A. Newman, J. Eagles, F. A. Mellon, and R. Greenwood. Am. J. Physiol. 275 (Endocrinol. Metab. 38): E717-E728, 1998]. We question ed whether, in healthy humans, D-glucose delivered intraluminally to t he midjejunum appeared systemically as extensively as that delivered i ntraduodenally. Subjects were infused over a period of 90 min with 50 g of glucose in 1 liter of isotonic saline (incorporating 0.5 g D-[C-1 3(6)]glucose) per 70 kg of body weight. Infusions were via enteral tub es terminating similar to 15 and 100 cm postpylorus. The systemic appe arance of glucose was monitored by means of a primed-continuous intrav enous infusion of D-[6,6-H-2(2)]glucose, Whereas 98 +/- 2% (n = 7) of the duodenally infused glucose appeared in the systemic circulation, o nly 35 +/- 9% (n = 7) of midjejunally infused glucose did so, implying that 65 +/- 9% was retained in the splanchnic bed. Either glucose was less efficiently absorbed at the midintestinal site or hepatic glucos e sequestration was increased 10-fold, or both. The proximal intestine plays a key role in the delivery of glucose to the systemic circulati on, and the distal intestine potentially delivers more glucose to the liver.