M1721 Role of Organic Cation Transporters (Oct1, Oct2 and Oct3) in the Uptake of the Duodenal Ulcerogen Cysteamine in Rat Duodenal Mucosa and in Rat Small Intestinal Epithelial Cell Line IEC-6: Use of siRNA Technology

Abstract

SGLT1 siRNA treated cells, n=3). Kinetic studies demonstrated that the mechanism of SGLT1 siRNA mediated stimulation of Na:H exchange in IEC-18 cells was secondary to a significant increase in the Vmax (10.0 ±1.1 nmol/mg protein/30 sec in control cells and 31.0 ± 2.5 in SGLT1 siRNA treated cells, n=3, p<0.05) without an alteration in the affinity of the exchanger for Na. RTQ-PCR demonstrated significant decrease in SGLT1 mRNA while NHE3 mRNA was significantly increased with SGLT1 siRNA treatment of IEC-18 cells. Western blot studies demonstrated that whereas SGLT1 protein was nearly absent NHE3 protein increased 2 fold SGLT1 siRNA treated IEC 18 cells. Conclusions: A reduction in BBM SGLT1 protein levels directly stimulates BBMNHE3 in IEC-18 cells. Themechanism of this stimulation is secondary to an increase in NHE3 transporter numbers. Thus, these data indicate that BBM SGLT compensatorily regulates BBM NHE3 in intestinal epithelial cells to maintain intracellular Na homeostasis.