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Renin-angiotensin system in the carotid body
Po Sing Leung1, Man Lung Fung, Michael S C Tam
1Department of Physiology, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China. psleung@cuhk.edu.hk
Abstract:
Research studies have been done on the influence of the renin-angiotensin system (RAS) on numerous tissues and organs. The local RAS, which is frequently of paracrine/autocrine origin, caters to specific organ and tissue needs through actions that add to, or differ from, the circulating RAS. Recent data have demonstrated a functional expression of RAS in the carotid body, wherein the carotid chemoreceptors play a major physiological role in the regulation of autonomic responses to changes in arterial chemical content. However, the angiotensin II and other vasoactive substances can directly modulate the excitability of the chemoreceptor. Long-term hypoxia modifies the level of gene expression in the carotid body by increasing the expression of AT(1) receptors along with sensitivity of the chemoreceptor to angiotensin II. Even though these findings support a physiological role of RAS in the carotid body, it has yet to be clearly defined. As a result this review will present current information about expression and localization of AT(1) receptors, and show that local RAS exists in the carotid body. The regulation of RAS by chronic hypoxia, the significance of its changes and clinical relevance in the carotid body, are also addressed.
Insights
The renin-angiotensin system (RAS) is present in the carotid body, influencing chemoreceptor function. Chronic hypoxia alters this system, impacting autonomic responses and highlighting its clinical relevance.
Area of Science:
- Physiology
- Cardiovascular Research
- Neuroendocrinology
Background:
- The renin-angiotensin system (RAS) influences various organs through local paracrine/autocrine actions.
- Recent studies indicate functional RAS expression within the carotid body, crucial for autonomic regulation.
Purpose of the Study:
- To review the expression and localization of angiotensin II type 1 (AT(1)) receptors in the carotid body.
- To demonstrate the existence of a local RAS within the carotid body.
- To explore the regulation of RAS by chronic hypoxia and its clinical significance.
Main Methods:
- Review of existing research on RAS components in the carotid body.
- Analysis of studies investigating AT(1) receptor expression and localization.
- Examination of data on hypoxia-induced changes in carotid body RAS.
Main Results:
- Evidence supports the presence and functional expression of RAS in the carotid body.
- Angiotensin II directly modulates carotid chemoreceptor excitability.
- Chronic hypoxia increases AT(1) receptor expression and chemoreceptor sensitivity to angiotensin II.
Conclusions:
- A local RAS exists in the carotid body, playing a physiological role in chemoreception.
- Hypoxia-induced alterations in carotid body RAS are significant and have potential clinical relevance.
- Further research is needed to fully define the role of RAS in carotid body function.