Abstract
ABSTRACT: The transport of phosphate into jejunal endoplasmic reticulum vesicles isolated from suckling and adolescent rats was investigated using a rapid filtration technique. Intestinal endoplasmic reticulum from both ages were enriched with NADPH cytochrome-C-reductase whereas other markers for brush border, basolateral, mitochondrial, and Golgi apparatus were impoverished. Phosphate uptake represented an energy-dependent process as evident by more than 80% decrease in uptake values at 0° C compared to 25° C. Phosphate uptake was ATP dependent in both age groups, however, mean uptake values were significantly greater in suckling rats compared to adolescent rats. pH optimum for uptake was 7.2. p-Chloromer-curibenzoate at 100 μM concentration inhibited phosphate uptake by more than 90%. Initial rate of phosphate uptake was linear up to 45s. Kinetics of phosphate uptake at 30 s showed a Km of 0.7 ± 0.1 and 0.15 ± 0.1 suckling and adolescent rats, respectively. Vmax was 1.5 ± 0.5 and 0.14 ± 0.01 nmol/mg protein/30 s for both suckling and adolescent rats, respectively. Herein we provide evidence for the first time for the presence of a phosphate carrier in intestinal endoplasmic reticulum of rats. Endoplasmic reticulum of phosphate uptake was significantly greater in suckling rats compared to adolescent rats. This increase in uptake is due to a greater number and activity of phosphate carriers in suckling rats.
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Ghishan, F., Arab, N. Phosphate Transport hy Intestinal Endoplasmic Reticulum during Maturation. Pediatr Res 23, 612–615 (1988). https://doi.org/10.1203/00006450-198806000-00017
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DOI: https://doi.org/10.1203/00006450-198806000-00017