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Abnormal fluid homeostasis in apelin receptor knockout mice
Emma M Roberts1, Michael J F Newson, George R Pope
1Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology, University of Bristol, Bristol BS1 3NY, UK.
The Journal of Endocrinology
|July 7, 2009
Summary
The apelin receptor (APJ) plays a key role in fluid balance. APJ knockout mice show reduced water intake and impaired urine concentration, indicating an anti-diuretic effect of apelin.
Area of Science:
- Neuroendocrinology
- Physiology
- Molecular Biology
Background:
- The apelinergic system, including apelin and its receptor APJ, is found in brain regions controlling fluid homeostasis.
- Its localization suggests a role in regulating arginine vasopressin (AVP) and drinking behavior.
Purpose of the Study:
- To investigate the physiological role of APJ in fluid balance regulation.
- To determine the impact of APJ deficiency on water intake, urine production, and AVP-mediated responses.
Main Methods:
- Utilized APJ knockout (APJ(-/-)) and wild-type mice in metabolic cages.
- Measured water intake, urine volume, and osmolality under normal and dehydration conditions.
- Analyzed plasma AVP levels and c-fos mRNA expression in specific brain nuclei.
Main Results:
- APJ(-/-) mice exhibited significantly lower water intake compared to wild-type mice.
- APJ(-/-) mice were unable to concentrate urine effectively after dehydration or desmopressin administration.
- Dehydration altered c-fos expression differently in APJ(-/-) mice within the subfornical organ and paraventricular nucleus.
Conclusions:
- APJ is physiologically important for regulating water intake and fluid retention.
- Apelin exerts an anti-diuretic effect in vivo, mediated partly through central mechanisms.
- The findings highlight APJ's role in the neuroendocrine control of body fluid homeostasis.
