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Parathyroid hormone (PTH), which is elevated in patients with chronic renal failure, has been shown to participate in the development of vascular calcification. Previous studies have demonstrated that PTH may promote endothelial expressions of proinflammatory parameters. On the basis of these data, we evaluated whether PTH may have an impact on endothelial osteoprotegerin (OPG), a vascular-protective factor which may control vascular calcification. Endothelial cells were stimulated with 10-12 to 10-10 mol/l PTH. PKC and PKA are the main cellular pathways of PTH. Inhibitors and activators of PKC or PKA were used to determine whether these signaling pathways are involved in the control of endothelial OPG. PTH induced a decrease in OPG secretion and mRNA expression. Treatment of PTH-stimulated cells by calphostin C (PKC inhibitor) induced a further decrease in OPG secretion, while Rp-cAMP (PKA inhibitor) had no additional effect. In nonstimulated cells, a PKC activator significantly stimulated OPG secretion, while a PKA activator was associated with a decline. These effects were blunted in the presence of calphostin C and Rp-cAMP, respectively. An increase in OPG secretion induced by a PKC activator indicates that the basal OPG secretion is mediated through PKC. The decrease induced by a PKA activator, which is similar to the decrease observed with PTH, suggests that the action of PTH on OPG secretion and mRNA expression may be due to the PKA pathway. [ABSTRACT FROM AUTHOR]

The necessity of withdrawal of aspirin [acetylsalicylic acid (ASA)] for fear of perioperative or postoperative bleeding in patients about to undergo surgery is as yet controversial. In this study we prospectively evaluated the effect of ASA on postoperative bleeding in end-stage renal failure patients who underwent insertion, removal, and/or replacement of a peritoneal dialysis (PD) catheter at our institution from November 1999 to March 2001. During the study period 52 of the above procedures were consecutively performed in 46 patients. Patients whose catheters were removed as a result of refractory peritonitis were excluded from the study. In all cases the PD catheter used was the coiled two-cuff Tenckhoff (NIPRO™, Manchester, GA) catheter and the surgery was performed in the operating room under local anesthesia. No drains were left in the operating wound. Postoperative bleeding (wound hematoma or persistent oozing from the incision or exit site) was classified as either minor (requiring no professional intervention and/or blood replacement) or major [necessitating blood transfusion (≥ 1 unit red blood cells). Of the 52 procedures 29 (in 24 patients) were performed while the patient was receiving aspirin at the time of operation (aspirin group). The remaining 23 were without aspirin and constituted the control group. ASA dose was 100 mg/day in all but three who were on buffered ASA (325 mg/day). The groups were well matched with regard to age; sex; mean residual renal function; and preoperative international normalized ratio, activated partial thromboplastin time, and platelet count. In no case was there significant intraoperative bleeding. There were five (17.2%) and three (13.0%) minor bleeds in the aspirin group and control group, respectively. One major bleed occurred in the control group ending in an exploratory laparotomy. Of the nine bleeding complications six were observed after catheter removal. From these data we conclude that PD catheter... [ABSTRACT FROM AUTHOR]