Abstract 516: Intestinal Cell Gastrin Secretion is Regulated by a Sodium-Induced Increase in PPAR-A that is Mediated by Dopaminergic Stimulation
Recently a novel gastro-renal axis has been discovered for the regulation of renal sodium excretion at the moment of sodium ingestion. Cells in the digestive track secrete gastrin in response to sodium ingestion which stimulates an increase in renal sodium excretion. Dopamine is largely responsible for the regulation of sodium excretion in the kidney, and has also been shown to decrease sodium transport in intestines. We hypothesized that dopamine might also be involved with the regulation of gastrin secretion in a human intestinal gastrin secreting cell line (SW626, ATCC, Manassas VA) that also contains dopaminergic receptors. We used the ionophore monensin (MON) to increase intracellular sodium in SW626 cells in order to simulate an oral sodium load. We also stimulated the cells with the dopaminergic agonist SKF38393 (SKF, D1-like receptor agonist). These two manipulations (compared to vehicle VEH) caused increased relative gene expression of gastrin (ΔΔCt gastrin to actin, VEH 0.00638±0.00283; MON 0.3913372±0.0985926; SKF 0.2139286±0.0253672; P<0.01 VEH vs MON or SKF, N=6 per group). Peroxisome proliferator-activated receptor-alpha (PPAR-α) associates with the gastrin transcriptional promoter by CHIP-SEQ (ENCODE database) and PPAR-α activation by fenofibrate (FENO) has been shown to reduce blood pressure and increase sodium excretion. We hypothesized that PPAR alpha would increase gastrin expression. FENO increased the immunoreactive gastrin and this effect was blocked by a PPAR alpha antagonist GW6471 (VEH 16,440±2,438 RFU; FENO 42,639±4,891; FENO+GW 19,367±1,865; P<0.001 VEH vs FENO and FENO vs FENO+GW). Stimulation with MON or SKF also significantly stimulated the production of immunoreactive gastrin (VEH 16,440±2,438 RFU; MON 22,345±935; SKF 24,386±1,124; GW alone 10,235±1,214; P<0.05 VEH vs MON, SKF, or GW, N=6). SW626 appear to secrete gastrin, therefore we tested the ability of secreted gastrin obtained from the media bathing SW626 cells to bind to i22 human renal proximal tubule cells (RPTC). After incubation of i22 RPTC in SW626 media for 24 hours, we detected surface gastrin staining on the i22 RPTC. We conclude that gastrin is produced by SW626 cells, is secreted into the growth media, and can bind to cell surface receptors on RPTC.
Author Disclosures: J.J. Gildea: None. C. Zhang: None. D. Bigler Wang: None. H.T. Tran: None. R.A. Felder: None.
- © 2014 by American Heart Association, Inc.