Ontogenic development of lamb intestinal sodium-glucose co-transporter is regulated by diet

• Published in: The Journal of physiology Vol. 437; no. 1; pp. 699 - 708
• Main Authors: SHIRAZI-BEECHEY, S. P, HIRAYAMA, B. A, WANG, Y, SCOTT, D, SMITH, M. W, WRIGHT, E. M
• Format: Journal Article
• Language: English
• Published: Oxford The Physiological Society 01.06.1991; Blackwell
• Subjects: Animals; Biological and medical sciences; Blotting, Western; Diet; Female; Fundamental and applied biological sciences. Psychology; Glucose - metabolism; Intestinal Absorption - physiology; Intestine, Small - growth & development; Intestine, Small - metabolism; Intestine. Mesentery; Kinetics; Male; Sheep - growth & development; Sodium - metabolism; Vertebrates: digestive system; Digestive system; Biological transport; Gut; Glucose; Postnatal development; Uptake; Proteins; Vertebrata; Brush border; Mammalia; Diet; Sodium; Immunoblotting assay; Sheep; Artiodactyla; Ungulata
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1113/jphysiol.1991.sp018620

1. The ontogenic development of the intestinal Na(+)-glucose co-transporter was measured in lambs as a function of diet. Transport activity was assayed in brush-border membrane vesicles and the expression of transport protein in the brush-border membrane determined by Western analysis. 2. Na(+)-dependent D-glucose transport increased to a maximum (300-700 pmol mg-1 s-1) within the first 2 weeks of birth and then declined to negligible amounts (less than 10 pmol mg-1 s-1) over the next 8 weeks. There was no further change over the next 2-3 years. Early changes were associated with modifications in both the maximum velocity Vmax for transport and expression of carrier protein in the brush-border plasma membrane. 3. Maintaining lambs on a milk replacer diet beyond the normal weaning period prevented the normal decline in the expression of Na(+)-glucose co-transport. At 5 weeks the transport rate was 433 +/- 150 pmol mg-1 s-1 in lambs maintained on milk replacer, but only 79 +/- 40 pmol mg-1 s-1 in normally reared control lambs. 4. Infusing the proximal intestine of 2- to 3-year-old sheep with 30 mM-D-glucose for four days increased the rate of transport 40- to 80-fold above that found in control animals perfused with mannitol. A similar but smaller increase was observed in one animal perfused with the non-metabolizable sugar alpha-methyl-D-glucopyranoside. The induced increase in glucose transport was correlated with the expression of the co-transporter protein in the brush-border plasma membrane. 5. It is concluded that the age-related decline in Na(+)-glucose co-transport in the sheep intestine is directly due to the decrease in D-glucose (and D-galactose) reaching the small intestine after development of the rumen. These results further suggest that luminal sugar substrates for the co-transporter promote both the maintenance and the up-regulation of the brush-border transport protein and it is the intact sugar itself which controls gene expression during enterocyte maturation.