ABSTRACT
OBJECTIVES: Elevated endothelin-1 (ET-1) levels have been detected during sepsis. The aim of the study was to examine the role of thromboxane A2 (TXA2) and ET-1 in pulmonary vascular reactions after endotoxin (LPS) challenge. DESIGN: Prospective experimental study in rabbits. SETTING: Experimental laboratory in a university teaching hospital. SUBJECTS: Twenty-four adult rabbits of either sex. INTERVENTIONS: Experiments were performed on 30 isolated and ventilated rabbit lungs, which were perfused with a saline solution containing 10% autologous blood. MEASUREMENTS AND MAIN RESULTS: Pulmonary arterial pressure and lung weight gain were continuously registered. Perfusate samples were drawn intermittently to determine ET-1, TXA2, and prostacyclin (PGI2) concentrations. LPS isolated from Escherichia coli (0.5 mg/mL; n = 6) was added to the perfusate. A marked pulmonary arterial pressure increase followed by massive edema formation after 60 mins was observed after LPS injection. At the same time, elevated TXA2 and PGI2 levels in the perfusate were measured. ET-1 was detected 30 mins after LPS infusion (13.4+/-2.6 fmol/L). Pretreatment with the ET(A) receptor antagonist LU135252 (10(-6) M; n = 6) almost completely suppressed the pressure reaction after endotoxin injection (p < .01 at 50 and 60 mins) and reduced edema formation (p < .05). The cyclooxygenase inhibitor diclofenac (10 microg/mL; n = 6) was as effective as LU135252 in preventing vascular reactions after LPS injection. CONCLUSIONS: Pretreatment with the ET(A) receptor antagonist LU135252 and the cyclooxygenase inhibitor diclofenac reduced pulmonary vascular reactions after LPS challenge. Based on the current data, we conclude that the pulmonary arterial pressure increase and edema formation after LPS injection are related to an ET-1- and TXA2-dependent mechanism.
Subject(s)
Endothelin Receptor Antagonists , Endothelin-1/blood , Phenylpropionates/pharmacology , Pulmonary Wedge Pressure/drug effects , Pyrimidines/pharmacology , Thromboxane A2/blood , Animals , Cyclooxygenase Inhibitors/pharmacology , Diclofenac/pharmacology , Endothelin-1/pharmacology , Endothelin-1/physiology , Female , Lipopolysaccharides/administration & dosage , Male , Prospective Studies , Pulmonary Artery/drug effects , Pulmonary Artery/physiology , Rabbits , Thromboxane A2/physiologyABSTRACT
Hemodialysis patients have a capacity for extrarenal production of 1 alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3]; however, the source of the hormone is unknown in these patients. Since 1,25(OH)2D3 synthesis by cultured hematopoietic cells has been demonstrated previously, we assessed hormone production by mononuclear cells from peripheral blood obtained from normal subjects (n = 6), uremic patients not yet requiring dialysis (n = 4) and hemodialysis patients (n = 14). 1,25(OH)2D3 production was analyzed by sequential straight phase and reverse phase HPLC. In the hemodialysis group, the mean specific production of a metabolite co-eluting with 1,25(OH)2D3 (in fmol/100,000 cells/h) both by monocyte-enriched adherent cells (Mo) and lymphocyte-enriched non-adherent cells (Ly) was increased as compared to non-dialyzed subjects (119 vs. 22 for Mo, not significant, 65 vs. 14 for Ly, p < 0.05). Taken together, Mo and Ly from hemodialysis patients synthesized significantly more 1,25(OH)2D3 (p < 0.02) than non-dialyzed subjects (184 vs. 36, means). No differences were found between cells from normal subjects and patients with preterminal renal failure. Exposure of cultured normal Mo (n = 6) to cuprophane (CU), polyacrylonitrile (AN69) or polycarbonate-polyether (PC) membrane devices resulted in increased 1,25(OH)2D3 production as compared to control incubations without membrane. The rank order of increase was PC > AN69 > CU, whereby only PC (p < 0.05) was significantly different from control. Our results suggest that blood mononuclear cells contribute to extrarenal 1,25(OH)2D3 synthesis in hemodialysis patients, and that this synthetic activity may be related to the hemodialysis procedures.