Is atrial natriuretic peptide important in the circadian rhythm of arterial blood pressure?

LETTERS Is Atrial Natriuretic Peptide Important in the Circadian Rhythm of Arterial Blood Pressure? It is well known that the arterial blood pressure (BP) presents a circadian rhythm,’ as do plasma renin activity (PRA) and plasma aldosterone.2 This rhythm also has been demonstrated for atria1 natriuretic peptide (ANP)3,4 secreted by atria1 cardiocytes and intimately involved in fluid, electrolyte and BP homeostasis.*g6 Six voluntary, clinically healthy, nonsmoking men were studied to estimate and eventually quantify the role of the circadian rhythms in ANP plasma levels on the genesis and conditioning of the circadian rhythm of the BP, together with the known relations to the PRA and plasma aldosterone. After a week of standard living conditions, with a normal sodium intake (130 mEq of sodium/day) with the subjects resting in a constant supine position, venous blood samples were drawn every 4 hours starting from midnight; BP was measured every 2 hours. Radioimmunologic methods were used to determine ANP,7 PRA,* and plasma aldosteroneg circulating levels, The mean f 1 SD have been calculated at each hour of sampling for the variables studied. The timerelated values have been subjected to circadian rhythmometric analysis by means of a “cosinor” method.‘O Figure 1 shows the circadian variations of ANP, PRA, plasma aldosterone and BP values. The cosinor analysis demonstrated a statistically significant (p
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crease of PRA and plasma aldosterone, which follows an increase of BP, also in relation to the increased sympathetic tone, in part ANP-induced.LL It is possible that the increased venous return may be

the main causal factor of the nighttime higher ANP levels, as demonstrated by the positive correlation between right atrial pressure and circulating levels of ANP.12 Our data suggest that the secretion of ANP, renin and aldosterone seem to have a chronologic sequence. Thus, the ANPPRA-plasma aldosterone axis can be considered as a single, chronobiologically coordinate system that regulates the water and sodium balance and the BP. Demenico Colantonio Pa010 Pasqualetti

Raffaele Casale Gianfranco

Natali

L’Aquila, Italy 14 November 1988 I

I

1. Carandente F, Halberg F. Chronobiology of blood pressure. Chronobiologia 1984;11:189341. 2. Katz FH, Romph D, Smith JA. Diurnal vari-

ation of plasma aldosterone, cortisol and renin activity in supine man. J Clin Endocrinol Metab 1975:40:125-134. 3. Donkier J, Anderson JV, Yeo T, Bloom SR. Diurnal rhythm in the plasma concentration of atria1 natriuretic peptide. N Engl J Med 1986; 315:710-711. 4. Colantonio D, CasaIe R, Desiati P, Di Lauro G, Pasqualetti P, Natali G. Ritmo circadian0 de1peptide natriuretico atriale nell’uomo sano. Cardiologia 1988;33:51 l-51 3. 5. Laragh JH. Atria1 natriuretic hormone, the renin-aldosterone axis, and blood pressure-electrolyte homeostasis. N Engl J Med 1985;313: 1330-l 340. 6. Needleman P, Greenwald JE. Atriopeptin: cardiac hormone intimately involved in fluid, electrolyte, and blood-pressure homeostasis. N Engl J Med 1986;314:828-834. 7. Jiippner H, Brabant G, Kapteina U, Kirschner M, Klein H, Hesch RD. Direct radioimmunoassay for human atria1 natriuretic peptide (hANP) and its clinical evaluation. Biochem Biophys Res Commun 1986:130:553-558. 8. Haber E, Koerner T, Page LE, Kliman B, Purnode A. Application of radioimmunoassay for angiotensin I to the physiologic measurements of olasma renin activitv in normal human subjects.‘J Clin Endocrinoi Metab 1969;29:

8 i 6 -a

4

s

2

a 0 =l 150 125 2

E 100

5 ;

75

1349-I

50 01

1,‘,‘,1,‘,‘11

12am 4am 8am 12pm 4pm 8plr FIGURE I. Circa&m

variation

(mean f

lstandarddwiation)ofbloodprers41re, atrial natriuretic peptide, plasmatic renin activity and plasma aldosterone in 6 clinically heaithy subjeds. ANP = atrial nat&wetic peptidq BP = blood pressure; PA = plasma aldoste#ww; PRA = plasma renin adivity.

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9. MacKenzie JK, Clements JA. Simplified radioimmunoassay for serum aldosterone utilizing increased antibody specificity. J Clin Endocrinol Metab 1974;38:622-627. 10. Nelson W, Tong YL, Lee JK, Halberg F. Method for cosinor rhythmometry. Chronobiologia 1979;6:305-323. il. Weidmann P, Hasler L, Gnadinger MP, Lang RE, Uehlinger DE, Shaw S, Rascher W, Reubi FC. Blood levels and renal effects of atrial natriuretic peptide in normal man. J Clin Invest 1986;77:734-742. 12. Richards AM, Cleland GF, Tonolo G, McIntyre GD, Leckie BJ, Dargie HJ, Ball SG, Robertson JI. Plasma alpha natriuretic peptide in cardiac impairment. Br J Med 1986;293: 409-412.