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This Article Full Text Full Text (PDF) All Versions of this Article: 290/2/E213    most recent 00158.2005v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Hayashi, M. Articles by Oiso, Y. Search for Related Content PubMed PubMed Citation Articles by Hayashi, M. Articles by Oiso, Y.

Vasopressin gene transcription increases in response to decreases in plasma volume, but not to increases in plasma osmolality, in chronically dehydrated rats

Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine, Nagoya, Japan

Submitted 8 April 2005 ; accepted in final form 31 August 2005

The synthesis of arginine vasopressin (AVP) in the magnocellular neurons of the supraoptic (SON) and paraventricular nuclei (PVN) is physiologically regulated by plasma osmolality and volume. To clarify how the regulation of AVP gene transcription is affected by chronic dehydration, we examined changes in the transcriptional activities of AVP gene by plasma osmolality and volume in both euhydrated and dehydrated conditions. Euhydrated rats had free access to water, whereas dehydrated rats had been deprived of water for 3 days before experiments. Rats in both conditions were subjected to acute hypertonic stimuli or hypovolemia, and changes in AVP heteronuclear (hn)RNA levels, an indicator of gene transcription, in the SON and PVN were examined with in situ hybridization. The intraperitoneal (ip) injection (2% body wt) of hypertonic (1.5 M) saline increased plasma Na levels by 40 meq/l in both euhydrated and dehydrated conditions. However, expression levels of AVP hnRNA in the SON and PVN were increased only in euhydrated, not dehydrated, rats. On the other hand, ip injection of polyethylene glycol decreased the plasma volume by 16–20%, and AVP hnRNA levels in the SON and PVN were significantly increased in both conditions. Thus it is demonstrated that signaling pathways regulating AVP gene transcription in the magnocellular neurons were completely refractory to acute osmotic stimuli under the chronic dehydration and that AVP gene transcription could probably respond to acute hypovolemia through different intracellular signal transduction pathways from those for osmoregulation.

dehydration; hyperosmolality; hypovolemia