AJP - Gastrointestinal and Liver Physiology, Vol 238, Issue 3 219-G227, Copyright © 1980 by American Physiological Society
Effects of nutrients, endogenous secretions, and fasting on in vitro glucose uptake
D. P. Kotler, G. M. Levine and Y. F. Shiau
The effect of luminal nutrients, endogenous secretions, and metabolic
balance on the initial velocity of glucose uptake was measured in everted
rings of rat intestine. Animals were fed either by total parenteral
nutrition (TPN), or into the midjejunum for 7 days, or fasted for 72 h.
Luminal feeding resulted in higher midjejunal glucose uptake per milligram
of protein, DNA, and centimeter gut length, when compared to fasting or
TPN. Kinetic analysis revealed a higher "apparent" Vmax in the luminally
fed group, whereas the "apparent" Km was similar in all groups. Diversion
of the pancreaticobility secretions did not affect glucose uptake in
luminally fed or TPN-fed animals. TPN-fed and fasted animals had similar
glucose uptake. Luminal feeding did not have a remote effect on glucose
uptake in intestine isolated from the nutrient stream. The results indicate
that luminal nutrients maintain carrier-mediated glucose transport after
direct contact with the mucosa. Overall metabolic balance and
pancreaticobiliary secretions do not affect carrier-mediated glucose
transport. The nutrient effect appears to involve an increased number of
glucose carriers per cell without a change in carrier affinity for glucose.
