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The medullipin system of blood pressure control
1Department of Pathology, University of Tennessee, Memphis.
Abstract:
The medullipin system of BP control has its cellular component in the renomedullary interstitial cells (RICs) of the renal papilla. The RICs secrete medullipin I which is conveyed to the liver to be activated into Med II. This activation appears to involve the cytochrome P-450 dependent enzyme system of the liver. Med II is a vasodilator that suppresses sympathetic tone, causes diuresis-natriuresis and has a suppressive effect on the central nervous system (CNS). As such, Med II has biologic actions the exact opposite of major actions of the renin-angiotensin system. Angiotensin II is a vasoconstrictor that facilitates sympathetic tone, causes salt water retention by the kidney and has stimulatory effect on the CNS. These are double feedback BP control systems. One elevates the BP and is prohypertensive; the other lowers BP and is antihypertensive. Unclipped (UC) the one-kidney, one-clip hypertensive rat has assisted greatly in elucidating the medullipin system. The support for these contentions are documented in this presentation.
Insights
The medullipin system, involving renomedullary interstitial cells (RICs), controls blood pressure (BP) by producing Med II, an antihypertensive hormone. This system opposes the prohypertensive renin-angiotensin system.
Area of Science:
- Nephrology
- Cardiovascular Physiology
- Endocrinology
Background:
- The kidney plays a crucial role in blood pressure (BP) regulation.
- The medullipin system, originating from renomedullary interstitial cells (RICs), is an endogenous antihypertensive system.
- This system counterbalances the prohypertensive renin-angiotensin system.
Purpose of the Study:
- To elucidate the cellular components and functions of the medullipin system in blood pressure control.
- To highlight the opposing actions of the medullipin system and the renin-angiotensin system.
- To underscore the significance of the medullipin system as a double feedback BP control mechanism.
Main Methods:
- Investigation of the medullipin system using the one-kidney, one-clip hypertensive rat model.
- Analysis of the cellular source (RICs) and activation pathway (liver, cytochrome P-450) of medullipins.
- Characterization of Med II's vasodilatory, sympathetic tone suppression, and diuretic-natriuretic effects.
Main Results:
- Renomedullary interstitial cells (RICs) secrete medullipin I, activated in the liver to Med II.
- Med II exhibits potent vasodilatory, antihypertensive, and natriuretic properties.
- Med II's actions are diametrically opposed to those of angiotensin II, demonstrating a dual BP regulation system.
Conclusions:
- The medullipin system acts as a critical antihypertensive counterbalance to the renin-angiotensin system.
- Understanding this dual system provides insights into novel therapeutic targets for hypertension.
- The one-kidney, one-clip rat model is instrumental in studying these complex BP regulatory mechanisms.
