DIURNAL RHYTHM OF NEUROPEPTIDE Y AND CATECHOLAMINES IN HYPERTENSIVE DIPPERS AND NON-DIPPERS: PP.32.259

Abstract

Objective: Causes of circadian blood pressure rhythm disturbances are not well understood. In hypertensive non-dippers increased catecholamines concentration was found. Neuropeptide Y (NPY) is potent neurotransmitter and mediator of the sympatho-adrenomedullary system, potentially involved in pathogenesis of hypertension. Therefore we investigated circadian rhythm of NPY in dippers (D) and nondippers (ND). Design and Methods: The study included 43 untreated hypertensive subjects (24F/19 M) in mean age 50 ± 11 yrs divided into 30 D and 13 ND. Blood samples for NPY, noradrenalin (NA) and adrenalin (A) were taken in 2, 6, 10 AM and 2, 6, 10 PM. Ambulatory blood pressure monitoring (SpaceLabs 20707) were performed in all patients. Results: Mean plasma NPY concentration during the day (dNPY) was compared to NPY at 2 PM (2NPY). In D dNPY was significantly higher than 2NPY (D 7,83 ± 2,99 vs 5,61 ± 3,35 fmol/ml; p < 0,0087). In ND dNPY was similar to 2NPY (8,37 ± 3,18 vs 7,33 ± 4,17 fmol/ml; NS). In D plasma 2NPY was higher, while in ND similar to NPY measured at 6AM, 10AM, 2 PM, 6 PM and 10PM. Plasma NA and A patterns were similar to that of NPY, respectively in D and ND. Plasma NA at 2 AM was higher in ND than in D (430 ± 308 vs 243 ± 160 pg/ml; p < 0,016). Analysis of variance showed circadian rhythm of NPY in D (F=3,77; p < 0,005) and did not in ND (F = 0,53;p = 0,746). Analysis also revealed circadian rhythm of NA and A in D and no in ND. Conclusion: Presented data showed that ND in contrast to D are characterized by abnormal circadian rhythm of NPY and catecholamines. It may suggest a role for NPY in development of non-dipping status in hypertensive patients.