Developmental regulation of Na⁺/H⁺exchanger expression in fetal and neonatal mice

Abstract

We examined the hypothesis that Na+/H+ exchanger expression is regulated during fetal and neonatal development and differentiation. To examine transcriptional regulation of the NHE1 isoform of the Na+/H+ exchanger, transgenic mice were created that contained the mouse NHE1 promoter driving expression of green fluorescent protein. The level of NHE1 transcription varied between tissues and with the stage of embryonic development. The highest expression was in the heart and liver of 12- to 15-day-old mice, and this declined with age. To examine Na+/H+exchanger protein levels, we immunoblotted mouse tissues from 18-day-old embryos, neonates, and adults. Protein levels increased after embryonic day 18 and peaked at 14 days of age in the heart, lung, liver, kidney, and brain. The greatest rise in NHE1 protein expression occurred in the heart, whereas the smallest increase was in the brain. The results suggest that Na+/H+ exchanger transcription and protein levels are controlled in a tissue-specific and time-dependent manner during development.

Mechanism of nicotinic acid transport in human liver cells: experiments with HepG2 cells and primary hepatocytes

“…These findings suggest the involvement of a nicotinic acid-H ϩ cotransport (and/or nicotinic acid/OH Ϫ exchange) process in the vitamin transport process in human liver cells. The source of H ϩ needed for driving nicotinic acid uptake into liver cells could be provided by the activity of Na ϩ /H ϩ exchangers, which are abundantly expressed in hepatocytes (4,11,21). In contrast to the role of incubation buffer pH (i.e., H ϩ ), no role for extracellular Na ϩ in nicotinic acid uptake by HepG2 cells was found, as isoosmotically replacing this monovalent cation with an equimolar concentration of other monovalent cations or with mannitol failed to affect the initial rate of uptake of this vitamin.…”

Dimeric Structure of Human Na+/H+ Exchanger Isoform 1 Overproduced in Saccharomyces cerevisiae

“…For SDS-PAGE and Western blotting, protein samples were heated at 65°C for 3 min and were separated on 10% SDS-polyacrylamide gels as described (27). For Western blot analysis, SDS-PAGE gels were transferred onto nitrocellulose membranes, and detection of recombinant hNHE1 was with HisProbe-HRP using the Supersignal West HisProbe Kit (Pierce) according to the manufacturer's instructions.…”

“…For Western blot analysis, SDS-PAGE gels were transferred onto nitrocellulose membranes, and detection of recombinant hNHE1 was with HisProbe-HRP using the Supersignal West HisProbe Kit (Pierce) according to the manufacturer's instructions. Alternatively, a monoclonal anti-NHE1 antibody was used as the primary antibody as described earlier (27) and peroxidase-conjugated goat anti-mouse antibody (Pierce) was used as a secondary antibody. X-ray films were digitized with an Epson (Toronto, ON) Perfection 3200 densitometer and bands were quantified using ImageQuant software (GE Healthcare Life Sciences).…”

Na+/H+exchanger isoform 1 facilitates cardiomyocyte embryonic stem cell differentiation

“…We have also found that NHE is developmentally regulated in the myocardium during development. Transcription from the NHE1 promoter was greatly elevated in the mouse heart embryo during development, and levels of expression of the NHE1 protein were elevated during heart development and immediately after birth (36,37). NHE1 message and activity have also been shown to be elevated in several models of cardiac hypertrophy (8,20,22), which is interesting since cardiac hypertrophy is characterized by a reactivation of the fetal gene program (1).…”