Dehydration Increases Angiotensin At1a But not At1b Mrna in Mouse Brain

Abstract

P3

Previous study showed that dehydration in mice produced an increase in brain ANG AT1 receptors. Because the receptor-binding assay can not distinguish the two AT1 receptors, AT1a and AT1b, we usedin situ hybridization methods to distinguish the ANG receptor mRNAs. Specific oligonucleotides probes from the 5’ or 3’ untranslated region of cDNA sequences were used. The objective was to determine the effect of 48-hr dehydration on AT1 mRNA expression in mouse brain. Plasma osmolality and hematocrit were increased after dehydration (349.6±6.1 vs 314.3±4.4 mOsm, p<0.01; 57.7±1.7 vs 46.9±1.4%, p<0.01). Paraformaldehyde fixed brains sections were processed for in situ hybridization using ³⁵S labeled probes. Analysis was conducted using a phosphor-imaging system and emulsion coated slides. There was specific labeling of areas known to contain Ang AT1 mRNA in rats, anteroventral third ventricle(AV3V), subfornical organ (SFO) and parvicellular paraventricular nucleus (PVN). The pattern of expression was similar for AT1a and AT1b. Dehydration produced an increase in AT1a mRNA in SFO, AV3V and PVN with no changes noted in lateral septal and anterodorsal nucleus. Dehydration produced no effect on AT1b expression. Results show 1) the localization pattern of Ang receptor subtypes in mouse brain with evidence for both AT1a and AT1b and 2) the specific effect of dehydration on AT1a mRNA.