Alveolar fluid clearance is driven by vectorial Na+ transport and promotes
postnatal lung adaptation. The effect of insulin on alveolar epithelial Na+
transport was studied in isolated alveolar cells from 18–19-day gestational age
rat fetuses. Equivalent short-circuit currents (ISC) were measured in Ussing
chambers and different kinase inhibitors were used to determine the pathway
of insulin stimulation. In Western Blot measurements the activation of mediators
stimulated by insulin was analyzed. The ISC showed a fast dose-dependent
increase by insulin, which could be attributed to an increased ENaC (epithelial
Na+ channel) activity in experiments with permeabilized apical or basolateral
membrane. 5-(N-Ethyl-N-isopropyl)amiloride inhibition of ISC was not
affected, however, benzamil-sensitive ISC was increased in insulin-stimulated
monolayers. The application of LY-294002 and Akti1/2 both completely
blocked the stimulating effect of insulin on ISC. PP242 partly blocked the
effect of insulin, whereas Rapamycin evoked no inhibition. Western Blot measurements
revealed an increased phosphorylation of AKT after insulin stimulation.
SGK1 activity was also increased by insulin as shown by Western Blot of
pNDRG1. However, in Ussing chamber measurements, GSK650394, an inhibitor
of SGK1 did not prevent the increase in ISC induced by insulin. The application
of IGF-1 mimicked the effect of insulin and increased the ENaC
activity. In addition, an increased autophosphorylation of the IGF-1R/IR was
observed after insulin stimulation. We conclude that insulin rapidly increases
epithelial Na+ transport by enhancing the activity of endogenous ENaC
through activation of PI3K/AKT in alveolar cells.
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa.de:bsz:15-qucosa-142643 |
| Date | 07 May 2014 |
| Creators | Mattes, Charlott, Thome, Ulrich H. |
| Contributors | Universität Leipzig, Division of Neonatology, Center for Pediatric Research Leipzig, Hospital for Children & Adolescents, Universität Leipzig, Division of Neonatology, Center for Pediatric Research Leipzig, Hospital for Children & Adolescents, Wiley, |
| Publisher | Universitätsbibliothek Leipzig |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | doc-type:article |
| Format | application/pdf |
| Source | Physiological Reports, 2 (3), 20 February 2014 doi: 10.1002/phy2.269 |
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