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Published on: October 26, 2020
Effect of apelin on glomerular hemodynamic function in the rat kidney
Annette Hus-Citharel1, Nadine Bouby, Alain Frugière
1INSERM, U 691, Paris, France.
Abstract:
Apelin is a vasoactive peptide identified as the endogenous ligand of an orphan G protein-coupled receptor called APJ. Apelin and its receptor have been found in the brain and the cardiovascular system. Here we show that the apelin receptor mRNA is highly expressed in the glomeruli while its level of expression is lower in all nephron segments including collecting ducts that express vasopressin V2 receptors. Intravenous injection of apelin 17 into lactating rats induced a significant diuresis. Apelin receptor mRNA was also found in endothelial and vascular smooth muscle cells of glomerular arterioles. Apelin administration caused vasorelaxation of angiotensin II-preconstricted efferent and afferent arterioles as shown by an increase in their diameter. Activation of endothelial apelin receptors caused release of nitric oxide which inhibited angiotensin II-induced rise in intracellular calcium. In addition, it appears that apelin had a direct receptor-mediated vasoconstrictive effect on vascular smooth muscle. These results show that apelin has complex effects on the pre- and post glomerular microvasculature regulating renal hemodynamics. Its role on tubular function (if any) remains to be determined.
Insights
Apelin, a peptide, influences kidney function by affecting blood vessels in the glomeruli. It causes vasodilation and has complex effects on renal hemodynamics.
Area of Science:
- Nephrology
- Cardiovascular Physiology
- Endocrinology
Background:
- Apelin is a vasoactive peptide and the endogenous ligand for the APJ receptor.
- Both apelin and its receptor are present in the brain and cardiovascular system.
- The expression patterns of apelin receptor in the kidney were previously unknown.
Purpose of the Study:
- To investigate the role of the apelin-APJ system in renal microcirculation and hemodynamics.
- To determine the localization and function of apelin receptors in the kidney.
Main Methods:
- Quantitative analysis of apelin receptor mRNA expression in rat kidney tissues.
- In vivo studies involving intravenous injection of apelin 17 in lactating rats.
- Ex vivo assessment of arteriolar responses to apelin administration using isolated rat glomeruli.
Main Results:
- Apelin receptor mRNA is highly expressed in glomeruli and vascular cells of glomerular arterioles.
- Apelin administration induced diuresis and vasorelaxation of afferent and efferent arterioles.
- Apelin activated nitric oxide release, inhibiting angiotensin II-induced calcium increase, but also exhibited a vasoconstrictive effect.
Conclusions:
- Apelin exerts complex, receptor-mediated effects on pre- and post-glomerular microvasculature, regulating renal hemodynamics.
- Apelin's precise role in tubular function requires further investigation.
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