OSR1-sensitive small intestinal Na+ transport

The oxidative stress responsive kinase 1 (OSR1) contributes to WNK (with no K)-dependent regulation of renal tubular salt transport, renal salt excretion, and blood pressure. Little is known, however, about a role of OSR1 in the regulation of intestinal salt transport. The present study thus explored whether OSR1 is expressed in intestinal tissue and whether small intestinal Na+/H+ exchanger (NHE), small intestinal Na+-glucose cotransport (SGLT1), and/or colonic epithelium Na+ channel (ENaC) differ between knockin mice carrying one allele of WNK-resistant OSR1 (osr1+/KI) and wild-type mice (osr1+/+). OSR1 protein abundance was determined by Western blotting, cytosolic pH from BCECF fluorescence, NHE activity from Na+-dependent realkalinization following an ammonium pulse, SGLT1 activity from glucose-induced current, and colonic ENaC activity from amiloride-sensitive transepithelial current in Ussing chamber experiments. As a result, OSR1 protein was expressed in small intestine of both osr1+/KI mice and o...