[Circadian rhythm of melatonin and blood pressure changes in patients with essential hypertension].

OBJECTIVE: To observe the association between melatonin (MLT) secretion and blood pressure changes during 24 hours in hypertensive patients (HPT) with (dipping) or without (non-dipping) night time blood pressure reduction. METHODS: The 24-hour blood pressure and urine 6-SMT (6-sulfatoxymelatonin, metabolism product of MLT in urine) in the daytime and nighttime were measured in normal control subjects (n = 20), non-dipping HPT group (n = 32) and dipping HPT group (n = 36). RESULTS: As expected, blood pressure reduction during the night was significantly lower in non-dipping HPT group compared to control and dipping HPT groups. Nighttime 6-SMT was significantly higher than daytime 6-SMT in all groups and nighttime urine 6-SMT levels and ratio of nighttime/daytime urine 6-SMT levels were significantly lower in non-dipping HPT group compared to control and dipping HPT groups (all P < 0.01). Moreover, ratio of nighttime/daytime urine 6-SMT levels are positively correlated blood pressure reduction during nighttime (P < 0.05) in all groups. CONCLUSIONS: Circadian rhythm of MLT secretion is maintained but nighttime MLT secretion was significantly reduced and related to disorders of circadian rhythm of blood pressure in non-dipping HPT group.

Evaluation of the biocompatibility of acellular porcine dermis.

The biocompatibility of an acellular porcine dermis was evaluated by in vitro methods. Endothelia cells (ECV-304) and fibroblasts (NIH-3T3) were seeded on the dermis and cultured for 1 week to assess the cell viability in the skin grafts. Results by morphological assessment and methylthiazolyl tetrazolium assay (MTT assay) indicated good biocompatibility of acellular porcine dermis, which allowed adhesion and proliferation of examined cell types. Flow chamber technique was used to evaluate the adhesive force between cells and biomaterials. There was no significant difference in cells retention ratio between control cells and experimental cells after sheared 24h. The determination of integrin alpha5 expression proved that the acellular porcine dermis did not influence the expression of integrin alpha5 in cells. The results suggested that the dermal equivalent made from pigskin is a promising material for burn treatment.