Age‐dependent regulation of sodium‐potassium adenosinetriphosphatase and sodium‐hydrogen exchanger mRNAs in equine nonglandular mucosa

Abstract

Gastric ulcers, common in young race horses, occur in the nonglandular (NG) region. Histopathology in tissues exposed to hydrochloric acid (HCl) and volatile fatty acids (VFAs) in vitro showed compromised sodium transport, likely regulated by cellular Na‐K‐ATP (NAKA) and/or Na‐H exchanger (NHE) enzymes. We determined relative gene expressions of NAKA and NHE in equine NG mucosa exposed to HCl and VFAs at three different pHs (1.5, 4, or 7.0). Five (≤5 yrs of age) and five (≥12 yrs of age) mixed breed and gender horses were used. NG mucosa near the Margo plicatus was collected and exposed in Ussing chambers to normal Ringer's solution (control), solution with a mixture of VFAs and solution with 40 mM of acetic acid (treatment). NAKA and NHE mRNA expressions were determined using real time PCR.We found increased expression of both target genes after exposure to VFAs, compared to controls. Interestingly, younger horses had significantly (P≤0.05) down‐regulated NAKA, while expression of NHE was increased. On the contrary, both NAKA and NHE were up‐regulated in older horses. Young horses may be more susceptible to gastric ulcers due to an inability to up‐regulate active sodium transport through NG mucosal cells. Novel treatments could be developed to enhance NG cell function and prevent gastric ulcers in horses. Funded by Centers of Excellence in Livestock Disease and Human Health, University of Tennessee.