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Development of brush-border membrane hexose transport system in chick jejunum
Insights
Hexose transport in chick jejunum develops rapidly after hatching, with phlorizin-sensitive glucose uptake increasing significantly by 2 days post-hatch. This indicates a critical developmental window for nutrient absorption in young chicks.
Area of Science:
- Nutritional Physiology
- Gastrointestinal Physiology
- Developmental Biology
Background:
- Hexose transport is crucial for nutrient absorption in the small intestine.
- Understanding the developmental changes in hexose transport is vital for avian nutrition and health.
- Previous studies have indicated developmental shifts in intestinal transport mechanisms.
Purpose of the Study:
- To characterize the developmental profile of hexose transport in chick jejunum.
- To investigate the role of phlorizin-sensitive transporters during chick development.
- To compare transport kinetics in jejunal slices and brush-border membrane vesicles.
Main Methods:
- Transport assays using 3-O-methyl-D-glucose in jejunal slices from chicks aged -2 to 21 days.
- Inhibition studies with phlorizin to identify transporter types.
- Analysis of Na-dependent D-glucose transport in jejunal brush-border membrane (BBM) vesicles.
- Kinetic analysis (Kt and Vmax) of phlorizin-sensitive and Na-dependent transport.
Main Results:
- Hexose uptake rates were low before hatching and at 0 days, increasing significantly by 2-7 days post-hatch.
- Phlorizin-sensitive hexose transport was absent in pre-hatch and 0-day chicks but accounted for ~80% of uptake in older chicks.
- Brush-border membrane vesicles showed higher Na-dependent D-glucose transport rates and Vmax in 2-day vs. 21-day-old chicks.
- Apparent Kt values for phlorizin-sensitive transport remained consistent, while Vmax increased with developmental age.
Conclusions:
- Chick jejunal hexose transport undergoes significant maturation post-hatch, with a rapid increase in phlorizin-sensitive transporter activity.
- The developmental upregulation of Vmax, rather than affinity (Kt), is a key feature of hexose transport maturation.
- These findings highlight a critical period for intestinal glucose absorption development in chicks, impacting early nutrition.
Abstract:
Hexose transport was characterized in jejunal slices and brush-border membrane (BBM) vesicles from chicks of several ages (range: 2 days before hatch to 21 days after hatch). With slices, initial rates of 0.1 mM 3-O-methyl-D-glucose transport were low in --2-, and 0-day chicks, increasing to maximal levels 2-7 days after hatching; rates declined to adult levels over the next 2 wk. Phlorizin did not inhibit uptakes in --2- or 0-day slices. In contrast, about 80% of the uptakes in tissue from 2-day or older chicks was phlorizin inhibitable. The apparent Kt for phlorizin-sensitive transport was the same in slices from 2- (maximal transport rates) and 21-day (minimal posthatch rates) chicks; the apparent Vmax was 2.5 times greater in 2-day slices. With BBM vesicles, initial rates of Na-dependent D-glucose transport and maximal overshoot levels were greater in 2-day vesicles than in 21-day vesicles. As in slice experiments, Kt values were the same in the two preparations, but Vmax values were 1.4 times higher in the 2-day preparation.