BLOOD PRESSURE 1994; 3: 355

EDITORIAL

Endothelin in Hypertension - a Matter Ignored or to Be Ignored?

Endothelin-1 (ET-l), which can be measured in the general circulation, has been suggested to play an autocrine/paracrine or even hormonal role in local vascular regulation [l]. As such it could be involved in the pathogenesis and maintenance of various forms of arterial hypertension, in analogy to its potential importance in pulmonary hypertension, where plasma endothelin levels are elevated [2].

However, in essential hypertension several studies have already reported that circulating endothelin levels are not increased [ 1,3-51. On the other hand, endothe- lin could still play an important pathogenetic role in renovascular hypertension in view of the vasoconstric- tive nature of this disease and the fact that elevated plasma endothelin levels have been described in renal failure [4]. The opinions in the literature on the importance of circulating endothelin in renovascular hypertension have so far been divided [6, 71.

In the present issue of BLOOD PRESSURE two renowned nephrology/hypertension research centers, independently of each other, address the issue of whether or not plasma endothelin levels are increased in patients with renovascular as well as essential hypertension [S, 91. Both studies provide further evidence that circulating endothelin is not elevated in patients with essential hypertension.

The two studies, one conducted in patients in whom antihypertensive therapy had been withdrawn for at least two weeks [S] and the other in which blood pressure lowering therapy was continued, with the exception of angiotensin converting enzyme inhibitors [9], are in full agreement also regarding circulating endothelin in patients with renal artery stenosis. Both studies show that plasma endothelin levels are not increased in patients with renovascular hypertension. The two studies also report significant renal extraction of endothelin, the exception being some small kidneys, not all, that actually released endothelin [S]. This release could not be explained by differences in blood supply to the kidneys.

Although the endothelin peptides represent some of the most potent endogenous vasoconstrictor agents currently known, there are as yet no clear evidence to indicate that they are involved in the pathogenesis of hypertension. However, the current rapid development of potent and selective endothelin receptor antagonists will hopefully help us to settle this issue more con- clusively within a near future.

Lennart Hansson Thomas Hedner

Sverker Jern

REFERENCES 1. Schiffrin EL, Thibault G. Plasma endothelin in human

essential hypertension. Am J Hypertens 1991; 4: 303-8. 2. Kaplan NM. Hormonal and local factors in hypertension.

Am J Med Sci 1991: 301: 412-20. 3. Kohno M. Yanusari K, Murakawa K et al. Plasma

immunoreactive endothelin levels in essential hyperten- sion. Am J Med 1990; 88: 614-8.

4. Shichiri M, Hirata Y, Ando K et al. Plasma endothelin levels in hypertension and chronic renal failure. Hyper- tension 1990; 15: 483-5.

5. Veglio F, Bertelio P, Pinna G, et al. Plasma endothelin levels in essential hypertension and diabetes mellitus.

6. Giussani M, Cianol M, Gazzano G, et al. High levels of angiotension can increase endothelin- 1 production in patients with renovascular hypertension. J Hypertens 1994; 12 (Suppl3): S192.

7. Yoshimi IM, Matsaushima Y, Kimura G, et al. Levels of endothelin-1 in renal venous and aortic plasma in patients with unilateral renovascular hypertension. J Hypertens 1994; 12(Suppl 3): S196.

8. Schreij G, van Es PN, Schiffers PMH, de Leeuw PW. Renal arterial and venous endothelin in hypertensive patients with or without renal artery stenosis. Blood Pressure 1994; 3: 370-4 (this issue).

9. Schwartz Serrensen S, Egeblad M, Eiskjerr H. Madsen B, Brerckner Nielsen C, Sihm I, Bjerregaard Pedersen E. Endothelin in renovascular and essential hypertension. Blood Pressure 1994; 3: 364-9 (this issue).

1993; 7: 321-6.

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