OBJECTIVES: In spite of broad interest, intensive studies on function of melatonin have not yielded much information about relationships between this hormone and kidneys in health, and particularity, in disease. Very little is known about the circadian plasma melatonin concentrations in patients with chronic renal failure (CRF). There are only a few studies dealing with melatonin concentrations in renal diseases, mainly performed in hemodialyzed patients with end-stage renal disease (ESRD). Moreover, the most melatonin assays were performed during the daytime, and the results are conflicting. Therefore, the aim of the present study was to determine the circadian melatonin profiles in patients with different stages of CRF.
MATERIAL AND METHODS: Twenty four patients (13 males and 11 females) with CRF aged 35 to 58 years (mean+/-SEM: 47.0+/-1.6 years) were included in the study. Patients were divided into two groups: group 1 -- patients with compensated CRF (serum creatinine: 2.0-5.0 mg/dL), group 2 -- patients with ESRD (serum creatinine: > 8,0 mg/dL). The control group consisted of 20 healthy volunteers (10 males and 10 females) aged 35 to 55 years (mean+/-SEM: 46.0+/-1.5 years) checked not to have renal failure [serum creatinine: 0.8-1.4 mg/dL], and matched according to sex and age. Blood samples were collected at 08:00, 12:00, 16:00, 20:00, 24:00, 02:00, 04:00, and 08:00 h. Melatonin concentration was measured by enzyme immunoassay.
RESULTS: In both groups of patients with chronic renal failure, i.e. in patients with compensated disease and in patients with end-stage renal disease melatonin nocturnal concentrations were significantly lower then those in healthy volunteers. Moreover, in patients with compensated renal failure also day-time melatonin concentrations were significantly depressed. Area under curve was significantly lower in both groups of patients in comparison with the control group.
CONCLUSIONS: The mechanism of depressed melatonin concentrations in CRF observed in our study remains unclear. However, it seems possible that decline in melatonin levels is due to impairment in adrenergic function that occurs in CRF. Because the studies on the melatonin secretion in CRF bring about conflicting results, the relationship between renal diseases and melatonin secretion needs further investigations.