Figure 5.

Nanoparticle-conjugated N3SP-1Δ7 stimulates NHE3 and reduces CTx-induced fluid secretion in vivo. (A) Closed-loop absorption studies of fluid absorption over 30 minutes in in vivo mouse proximal small intestine after 4-hour exposure to nanoparticle-peptide (400 nmol/L) demonstrated that N3SP-1Δ7 compared with CP-2 increased fluid absorption. (B) The N3SP-1Δ7 increased baseline fluid absorption was prevented by pretreatment with 10 μmol/L tenapanor (n = 4 and 3 separate experiments for A and B, respectively, with 8 animals studied for A and 12 for B). (C) At 4 hours after CTx (0.1 μg) exposure, net fluid secretion was determined in ileal loops also inoculated only with PBS, nanoparticles–CP-2 (4 μmol/L) or nanoparticles–N3SP-1Δ7 (4 μmol/L) (n = 6). P values compared with PBS/CTx loops by unpaired t tests. In parallel, ileal loops only exposed to PBS represent an additional control (n = 5). Data are shown as the mean ± standard error of the mean.