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Maturation of jejunal phosphate transport by rat brush border membrane vesicles
Insights
Phosphate transport in rat jejunum changes with age. Younger suckling rats show higher active and passive phosphate uptake compared to older rats, indicating maturational changes in jejunal phosphate absorption.
Area of Science:
- Physiology
- Gastroenterology
- Nutritional Science
Background:
- Phosphate is essential for numerous physiological processes.
- Jejunal absorption plays a critical role in maintaining phosphate homeostasis.
- Understanding age-related changes in intestinal phosphate transport is crucial for nutritional management.
Purpose of the Study:
- To investigate the maturational changes in jejunal phosphate transport in rats.
- To characterize the sodium-dependent and passive components of phosphate uptake.
- To compare phosphate transport activity between suckling and adult rats.
Main Methods:
- Isolation of jejunal brush border membrane vesicles.
- Utilized a rapid filtration technique to measure phosphate uptake.
- Investigated the effect of sodium gradients and valinomycin on phosphate transport.
Main Results:
- Phosphate uptake was enhanced by a sodium gradient across all ages studied.
- Both sodium-dependent and passive phosphate uptake decreased with increasing age.
- The activity of the sodium/phosphate cotransporter was significantly higher in 14-day-old suckling rats compared to 42-day-old adult rats.
- Phosphate uptake was found to be electroneutral at pH 7.4 in both age groups.
Conclusions:
- Jejunal phosphate transport undergoes significant maturational changes from suckling to adulthood.
- Suckling rats exhibit significantly higher jejunal phosphate transport than adult rats.
- Increased phosphate uptake in younger animals is attributed to enhanced active transport and increased passive permeability.
Abstract:
The transport of phosphate into jejunal brush border membrane vesicles isolated from 14- to 42-day-old rats was investigated using a rapid filtration technique. The presence of a sodium gradient enhanced phosphate uptake at all ages. Both sodium-dependent phosphate uptake and passive phosphate uptake declined with increasing age. The activity of the sodium/phosphate cotransporter was significantly greater in the 14-day-old suckling animals than in the 42-day-old animals. Experiments with valinomycin in 14- and 42-day-old animals showed that at pH 7.4, phosphate uptake is electroneutral at both ages. These findings demonstrate there are maturational changes in the jejunal transport of phosphate. Suckling animals transport significantly more phosphate than adult animals. The increased uptake in the younger animals is related to an increase in the active uptake of phosphate and an increase in the passive permeability to phosphate.