Partial sequence and expression of the gene for and activity of the sodium glucose transporter in the small intestine of fed, starved and refed chickens

A 970 bp cDNA Na⁺/glucose cotransporter (SGLT1) was isolated and sequenced from chicken jejunum by reverse transcriptase polymerase chain reaction (RT-PCR) using primers based on conserved regions. Using the 970 bp PCR product as a specific probe, Northern Blot hybridization indicated a transcript of ca. 4 kb. The isolated chicken intestinal SGLT1 cDNA was used to quantitate mRNA expression. Glucose uptake activity and kinetics were determined in brush border membrane vesicles (BBMV) from jejunum tissue of chickens which were either fed, food-deprived or refed following food deprivation. Net glucose uptake to BBMV was higher (P < 0.02) in the control and refed chicks (149 ± 11.9, 139.6 ± 7.43 pmol · mg protein^-1 · s^-1) than in food-deprived chicks (107 ± 4.23 pmol · mg protein^-1 · s^-1). The k(m) (150 μmol/L) and Vmax (1111.1 pmol · mg protein^-1 · s^-1) were higher in the food-deprived chicks compared to control and refed birds (25, 24 μmol/L and 227, 142 pmol · mg protein^-1 · s^-1, respectively). Expression of SGLT1 mRNA was significantly enhanced in the food-deprived and refed birds. In food-deprived chicks the lower affinity and higher activity of the SGLT1 transporter for glucose were accompanied by higher expression of mRNA which might indicate that the transporter was upregulated by low substrate concentration. Quantification of expression of intestinal mRNA of SGLT1 provides important information concerning control of nutrient uptake.