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Aortic Vasodilating Factor: A New
Cardiovascular Hormone?

Zeana, C.*; Botea, M; Calin, D**

*Medical Clinic, Emergency Hospital
**
Victor Babes Institute Bucharest, Romania

SUMMARY
Preamble : A complex neurohumoral mechanism promptly adapt the blood pressure to the necessities of the organism.
Hypothesis: Aorta is not only an elastic buffer of the systolic BP and an autonomic nervous baroreceptor but also is able to produce humoraql vasodilating factor(s).
Material and methods: Rabbit, Wistar rat and bovine aorta homogenates in Hanks solution supplemented with glucose, centrifugation, dialysis, concentration. a) This aortic extract (AE) was applied on segments of rat mesenteric arterioles and the diameter of the vessel was micrometrically determined. b) the 45 Ca Cl2, 3H cortisole,serotonine and noradrenaline admission in the rat myocardium and aortic wall incubated with AE were studied.
Results: AE from different species induced a significant arteriolar relaxation as well as an enhancement of noradrenaline and cortisol incorporation in the myocardium and aortic wall. The AE from young animals were more active (30% difference).
Discussion: The aortic wall seems to be more important in the BP control than formerly believed. The capacity of the aorta to produce this factor diminishes with the age. The influence of the AE on the Ca and some hormones incorporation into the myocardium and aorta is difficult to explain.
Conclusion: The aorta produces a vasodilating factor influencing the resistance vessels.

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   The pathogenesis of the primary arterial hypertension is complex and not completely clarified (1). The rest pressional homeostasis as well as the prompt adaptation of the blood pressure to the momentary necessities of the organism (physical activity, mental stress etc) is controlled by a complex integrated system involving nervous and humoral segments. The most important progress in understanding hypertension concerns the role of the genetic predisposition, of the sympatic nervous system and of the humoral factors such as renin-angiotensin system, corticosteroids and defects in the cell transport and binding of natrium and other substances. Aorta is considered to play a passive role in blood pressure regulation due to the elastic compliance of the aortic wall.

HYPOTHESIS
   Aorta Is not only an elastic buffer of the systolic elevation of the blood pressure and an autonomous nervous system baroreceptor zone but is also able to synthesize, store and release humoral factors in the context of the cardiovascular intrinsic regulatory mechanisms of the blood pressure. The atrial natriuretic hormone (2) is probably not the unique cardiovascular hormone.

MATERIAL AND METHODS
     The aortic extract (AE) was obtained from rabbit, wistar rat and bovine aorta. The aortic fragments in Hanks solution supplemented with glucose were subjected to homogenization, centrifugated for 10 minutes at 4000 rotations\min and then concentrated in vacuum for 48 hour. The vasomotor influence of the AE was studied

1) directly, by microscopic micrometry a) in vivo, on the exposed rat mesenteric arterioles and b) in vitro, on mesenteric arteriole segments.
2) Indirectly: radioactive calcium (as chlorure), 3HCortisol, 3HSerotonine and 3HNoradrenaline admission in the rat myocardium and aortic wall incubated in Hanks medium and supplemented with AE.

RESULTS
   The AE obtained from different species induced invariably vasodilatation no matter of the animal of origin (Table 1)
2 AE altered the above mentioned substances incorporation in the myocardium and aortic wall (Table 2)
The AE obtained from young animals proved to be by approx 30% more active than that obtained from old animals.



DISCUSSION
   The aorta seems to be more important in the blood pressure control than formerly believed. The aortic wall might synthetise humoral factor (s) with vasodilator properties. Probably the aortic distension is the stimulus to release this factor (s) that may plays a role in buffering the blood pressure elevations. This factor synthesis diminishes during the aging process and this may explain the tendency of elderly people to develop prolonged hypertensive states. It is difficult to explain the influence of the AE on the Calcium and some hormones incorporation into the myocardium and aorta.

CONCLUSIONS

1.The aorta synthetises a vasodilator factor(s).
2.The production of this cardiovascular hormone declines with age.

REFERENCES

1. Kaplan N D. Systemic hypertension: mechanism and diagnosis. in Braunwald E., Heart Disease. W Saunders Co, Philadelphia 1992, 826

2. Talartschik J , Eisenhauer T , Schroder I et al. Low atrial natriuretic peptide plasma concentrations in 100 patients with essential hypertension. Am. J. Hypertens 3:45, 1990.

 

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2nd Virtual Congress of Cardiology

Dr. Florencio Garófalo
Steering Committee
President
Dr. Raúl Bretal
Scientific Committee
President
Dr. Armando Pacher
Technical Committee - CETIFAC
President
fgaro@fac.org.ar
fgaro@satlink.com
rbretal@fac.org.ar
rbretal@netverk.com.ar
apacher@fac.org.ar
apacher@satlink.com

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