CIRCADIAN-RHYTHMS OF PLASMA ATRIOPEPTIN, PLASMA-RENIN ACTIVITY AND PLASMA-ALDOSTERONE IN PATIENTS WITH HEPATORENAL-SYNDROME

The etiology of hepatorenal syndrome (HRS) is still incompletely under stood, but the atriopeptin-renin-aldosterone system plays an important role in its pathogenesis. Since this system presents a circadian rhyt hmicity, the aim of the study was to investigate the circadian rhythm in the circulating concentrations (atrial natriuretic peptide, pANP), plasma renin activity (PRA) and plasma aldosterone (pA) in patients wi th HRS, compared with healthy controls. Venous blood samples were draw n during the span of a whole day and every two hours from a peripheral vein in 10 healthy subjects and in 10 patients with HRS. The circulat ing concentrations of pANP, PRA and pA were determined by radioimmunoa ssay. Statistical analysis was carried out by the ''cosinor'' method. The controls presented a significant (p<0.05) circadian rhythm for eac h variable, whereas no rhythm (p>0.05) was found in HRS patients. The pANP, PRA and pA rhythms were significantly (p<0.05) different between the two groups, HRS patients having higher mean daily concentrations and larger circadian variations of pANP, PRA and pA than controls. Sig nificant relations (p<0.05) were demonstrated between the mean daily c oncentrations of pANP and PRA (r=-0.79), PRA and pA (r=-0.73) and PRA and pA (r=0.76) in the controls; on the contrary, the HRS patients sho wed only a significant (p<0.05) positive relation between pANP and PRA (r=0.71). These results confirm the previous observation that the atr iopeptin-renin-aldosterone system presents a well-defined circadian ti me structure in healthy subjects, while the HRS patients present a com plete loss of the secretory sequentiality and of the circadian rhythm, with desynchronization of the whole system. This great upset in the t emporal and functional organizations of the system could play an impor tant role in promoting and/or in maintaining the hydro-electrolyte unb alance of HRS.