calcimycin and Kidney-Failure--Chronic

We examined the mechanism of endothelial dysfunction in chronic renal failure (CRF), with reference to NO synthase. CRF was induced by 5/6 nephrectomy in rats. Either L-arginine (1.25 g/L in drinking water), tetrahydrobiopterin (BH4, 10 mg/kg per day in food), or a combination of the 2 were orally administered to CRF rats for 9 weeks. CRF rats showed elevation of systolic blood pressure compared with sham-operated rats. Endothelium-dependent relaxation induced by acetylcholine or A23187 in the isolated aorta was significantly reduced, and in vitro treatment with L-arginine, BH4, or superoxide dismutase restored the relaxation. Aortic segments from CRF rats showed significantly higher superoxide production in response to A23187, which was inhibited by L-NAME. Plasma concentrations of asymmetric dimethylarginine and symmetric dimethylarginine were higher in CRF rats. These changes in CRF rats were totally or partially decreased by L-arginine or BH4 supplementation in vivo. Interestingly, the combined treatment showed additive effects in certain parameters. These results suggest that vascular disorders in CRF rats may be partly due to NOS uncoupling caused by a relative deficiency of BH4 and partially due to accumulation of endogenous inhibitors of NOS and L-arginine uptake, resulting in the decrease of NO production and the increase of reactive oxygen species.

Topics: Acetylcholine; Administration, Oral; Animals; Aorta; Arginine; Biopterins; Blood Pressure; Calcimycin; Drug Synergism; Drug Therapy, Combination; Endothelium, Vascular; Kidney Failure, Chronic; Male; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase Type III; Rats; Rats, Sprague-Dawley; Superoxide Dismutase; Superoxides

Platelets of patients with uremia develop a defective platelet function and have a decreased production of thromboxane B2 (TxB2). Activated platelets generate thromboxane from free arachidonate that is previously released from the membrane phospholipids (PLs) by phospholipases. Phospholipase A2 (PLA2) release up to 70% of the arachidonate in normal platelets, and to date, the activity of this enzyme in uremia is unknown. This work studied the PLA2 activity in the platelets of nine uremic patients and nine healthy volunteers. Washed platelets were labelled with [(14)C]arachidonic acid and activated with calcium ionophore A-23187 (4 microgr/ml). Lipids were resolved by TLC and identified by autoradiography. The distribution of [(14)C]arachidonic acid in the five major platelet phospholipids was found to be normal. Uremic platelets released more radioactivity than normal platelets (19.0 +/- 5.2% versus 11.3 +/- 1.6%, P = 0.001). The production of both, radioactive thromboxane B2 and hydroxyheptadecatrienoic acid was normal (2.6 +/- 1.2% and 3.5 +/- 1.6% of total radioactivity respectively), but the formation of the lipoxygenase metabolite hydroxyeicosatetraenoic acid was increased with respect to the controls (12.9 +/- 4.6% vs 7.0 +/- 1.3% of total radioactivity, P = 0002). In conclusion, platelets of patients with uremia have an increased activity of phospholipase A2 and produce increased amounts of hydroxyeicosatetraenoic acid, an inhibitor of the platelet function.

Topics: Arachidonic Acid; Blood Platelets; Calcimycin; Case-Control Studies; Fatty Acids, Unsaturated; Humans; Kidney Failure, Chronic; Phospholipases A; Phospholipases A2; Platelet Function Tests; Thromboxane B2; Uremia

Complement activation (plasma levels of the anaphylatoxins C3a and C5a), the aggregation of polymorphonuclear neutrophils (PMN) on 12-O-tetradecanoyl-4 beta-phorbol-13-acetate (TPA) 2.5 microM, A23187 5 microM, arachidonic acid 0.1 mM and TPA-induced thromboxane A2 production by PMN were examined in 10 uraemic patients at times 0, 15 and 240 min after the onset of haemodialysis with Cuprophan (CU) and polyacrylonitrile (PAN) membranes. The rise in plasma C3a and C5a was intense during haemodialysis with CU, but mild with PAN. PMN aggregation in uraemic patients was lower (as compared to normal controls) independently of the agonist used. At 15 min of haemodialysis with CU, PMN aggregation increased and decreased at 240 min, while during haemodialysis on PAN no significant changes in PMN aggregation were noticed. TPA-induced TxA2 synthesis by PMN was decreased in uraemic patients. It was normalized after haemodialysis with PAN, but not with CU. Apparently the mechanisms underlying PMN aggregation and TxA2 synthesis during haemodialysis may not be entirely dependent on complement activation. Evidently, dialysable plasma factors may be responsible for the abnormal PMN function in uraemic patients. Thus, removal of these factors by haemodialysis with an appropriate membrane may improve the PMN functions.

Topics: Acrylic Resins; Adult; Arachidonic Acid; Calcimycin; Cell Aggregation; Cellulose; Complement Activation; Humans; Kidney Failure, Chronic; Membranes, Artificial; Middle Aged; Neutrophils; Renal Dialysis; Tetradecanoylphorbol Acetate; Thromboxane A2; Thromboxane B2

Available data indicate that B cell proliferation is inhibited in chronic renal failure and this is due to excess blood levels of PTH. This defect may also affect immunoglobulin production. We examined production of IgG, IgM and IgA by B cells stimulated with Staphylococcus aureus Cowan I (SAC) or with pokeweed mitogen (PWM) after eight days of culture and evaluated the effect of PTH on this process in 34 hemodialysis patients and 44 normal subjects. IgG, IgM and IgA production by B cells from patients was lower (P less than 0.01) than by B cells from normal subjects. Both 1-34 and 1-84 PTH inhibited (P less than 0.01) immunoglobulin production by B cells from normal subjects and dialysis patients. However, this inhibitory effect was evident in dialysis patients only with the higher dose of PTH. The inhibition of immunoglobulin production by PTH occurred only when the hormone was added at the initiation of the B cell culture. Inactivation of PTH abolished its inhibitory effect on immunoglobulin production. Agents that stimulate cAMP production (forskolin, cholera toxin) and the cAMP analogue, 8-bromoadenosine 3',5' cyclic monophosphate inhibited immunoglobulin production by B cells from both normal and dialysis patients, and the degree of inhibition was not different between the two groups. The calcium inophore A23187 also inhibited IgG, IgA and IgM production by B cells from normal subjects and dialysis patients; there was no significant difference in the degree of inhibition between the two groups. The resting levels of cytosolic calcium in B cells of dialysis patients was significantly (P less than 0.01) higher than that of B cells from normal subjects. The data show that: (1) immunoglobulin production is impaired in dialysis patients; (2) B cells of dialysis patients have elevated resting levels of cytosolic calcium; (3) PTH inhibits IgG, IgA and IgM production and this effect is at least partly mediated by PTH-induced cAMP production and alterations in cytosolic calcium into B cells; (4) this inhibitory effect is mediated by events that affect initial stages of B cell proliferation and maturation; (5) the requirement for high dose of PTH for its inhibitory effect on B cells from dialysis patients is probably due to desensitization and/or down-regulation of PTH receptors on B cells. The results are consistent with the proposition that impaired immunoglobulin production by B cells from dialysis patients is at least partly due to the state of secondary

Topics: 8-Bromo Cyclic Adenosine Monophosphate; Adult; Antibody Formation; B-Lymphocytes; Calcimycin; Calcium; Cholera Toxin; Colforsin; Female; Humans; Immunoglobulins; Kidney Failure, Chronic; Male; Middle Aged; Parathyroid Hormone; Pokeweed Mitogens; Staphylococcal Infections

Topics: 6-Ketoprostaglandin F1 alpha; Calcimycin; Humans; Kidney Failure, Chronic; Macrophages; Methacrylates; Peritoneal Dialysis, Continuous Ambulatory; Thromboxane B2; Thromboxane-A Synthase; Thromboxanes