Apically expressed intestinal and renal sodium-hydrogen exchangers (NHEs) play a major role in Na(+) absorption. Our previous studies on NHE ontogeny have shown that NHE-2 and NHE-3 are expressed at very low levels in young animals. Furthermore, single and/or double NHE-2 and NHE-3 knockout mice display no obvious abnormalities before weaning. These observations suggest that other transporter(s...

Bicarbonate and butyrate stimulate electroneutral Na absorption via apical membrane Na-H exchange (NHE) in rat distal colon. cAMP downregulates NHE-3 isoform and inhibits HCO3-dependent, but not butyrate-dependent, Na absorption. This study sought to determine whether 1) the apical membrane NHE-2 and NHE-3 isoforms differentially mediated HCO3- and butyrate-dependent Na absorption, and 2) cAMP ...

Parathyroid hormone (PTH) is a potent inhibitor of mammalian renal proximal tubule sodium absorption via suppression of the apical membrane Na/H exchanger (NHE-3). We examined the mechanisms by which PTH inhibits NHE-3 activity by giving an acute intravenous PTH bolus to parathyroidectomized rats. Parathyroidectomy per se increased apical membrane NHE-3 activity and antigen. Acute infusion of P...

The Na(+)-H+ exchanger has important modulatory effects on vascular smooth muscle cell proliferation and contractility. Increased Na(+)-H+ exchange activity is a general property of many tissues, including mesenteric artery and cultured vascular smooth muscle cells, in the spontaneously hypertensive rat (SHR). In the present work, we investigated whether alterations in the steady-state levels o...

Chronic metabolic acidosis (CMA) is associated with an adaptive increase in the bicarbonate absorptive capacity of the rat medullary thick ascending limb (MTAL). To specify whether NHE-3, the apical MTAL Na/H exchanger, is involved in this adaptation, NHE-3 mRNA was quantified by a competitive RT-PCR using an internal standard which differed from the wild-type NHE-3 mRNA by an 80-bp deletion. C...

The present studies examined the effects of chronic NaCl administration and metabolic alkalosis on NHE-3, an apical Na+/H+exchanger of the rat medullary thick ascending limb of Henle (MTAL). NaCl administration had no effect on NHE-3 mRNA abundance as assessed by competitive RT-PCR, as well as on NHE-3 transport activity estimated from the Na+-dependent cell pH recovery of Na+-depleted acidifie...

Molecular cloning, tissue distribution and ontogenetic regulation of sodium/proton exchanger isoform 2 (NHE-2) mRNA expression were evaluated in the pig small intestine during postnatal development. The 2872-bp porcine full cDNA sequence of the NHE-2 (EF672046) cloned in this study showed 80% and 70% homology with known human and mouse gene sequence, respectively. Hydrophobic prediction suggest...

We tested the effects of epidermal growth factor (EGF) on Na+/H+ exchanger (NHE) activity using urogastrone for treatment of Wistar rats and rat kidney tissue slices. NHE activity was monitored in isolated kidney brush border membrane vesicles by following fluorescence quenching of acridine orange. A significant increase of NHE activity was detected as early as 5 min after addition of urogastro...

Na-H exchange (NHE) is one of the major non-nutritive Na absorptive pathways of the intestine and kidney. Of the four NHE isoforms that have been cloned, only one, NHE-3, appears to be epithelial specific. We have examined the regional and cellular expression of NHE-3 in the rat intestine. NHE-3 message in the small intestine was more abundant in the villus fractions of the small intestine than...

Cardiac hypertrophy (CH) is a major risk factor for cardiac death and commonly precedes the development of heart failure (HF). This is motivating the search for novel pharmacological strategies to prevent the development and/or regress CH. Although the signaling pathways leading to myocardial hypertrophy are complex, one important set of pathways involves the mitogen-activated protein kinases (...