Effect of a cyclooxygenase-2 inhibitor on postexercise muscle protein synthesis in humans.

Nonselective blockade of the cyclooxygenase (COX) enzymes in skeletal muscle eliminates the normal increase in muscle protein synthesis following resistance exercise. The current study tested the hypothesis that this COX-mediated increase in postexercise muscle protein synthesis is regulated specifically by the COX-2 isoform. Sixteen males (23 +/- 1 yr) were randomly assigned to one of two groups that received three doses of either a selective COX-2 inhibitor (celecoxib; 200 mg/dose, 600 mg total) or a placebo in double-blind fashion during the 24 h following a single bout of knee extensor resistance exercise. At rest and 24 h postexercise, skeletal muscle protein fractional synthesis rate (FSR) was measured using a primed constant infusion of [(2)H(5)]phenylalanine coupled with muscle biopsies of the vastus lateralis, and measurements were made of mRNA and protein expression of COX-1 and COX-2. Mixed muscle protein FSR in response to exercise (P < 0.05) was not suppressed by the COX-2 inhibitor (0.056 +/- 0.004 to 0.108 +/- 0.014%/h) compared with placebo (0.074 +/- 0.004 to 0.091 +/- 0.005%/h), nor was there any difference (P > 0.05) between the placebo and COX-2 inhibitor postexercise when controlling for resting FSR. The COX-2 inhibitor did not influence COX-1 mRNA, COX-1 protein, or COX-2 protein levels, whereas it did increase (P < 0.05) COX-2 mRNA (3.0 +/- 0.9-fold) compared with placebo (1.3 +/- 0.3-fold). It appears that the elimination of the postexercise muscle protein synthesis response by nonselective COX inhibitors is not solely due to COX-2 isoform blockade. Furthermore, the current data suggest that the COX-1 enzyme is likely the main isoform responsible for the COX-mediated increase in muscle protein synthesis following resistance exercise in humans.

Sensitization of renal transplant candidates by cryopreserved cadaveric venous or arterial allografts.

BACKGROUND: Cryopreserved cadaveric venous or arterial allografts are used in ESRD patients as an alternative to synthetic grafts for hemodialysis access. We evaluated the effect of these allografts on the PRA against HLA class I and II antigens in 11 ESRD patients awaiting a kidney transplant. METHODS: Flow Cytometry using purified antigen coated beads (Flow PRA Beads) was used to determine PRA against HLA class I and II antigens. RESULTS: Patients with no antibody prior to allograft implantation were all positive for HLA class I and II antibodies after implantation. Patients with anti-HLA class I and II antibodies prior to allografting, developed higher antibody titers. Of the 11 patients that received cryopreserved cadaveric allografts no deaths were reported. Two grafts were removed due to thrombosis consistent with rejection. CONCLUSION: Recipients of cadaveric venous or arterial allografts elicit an HLA antibody response attesting to the antigenicity of cryopreserved cadaveric allografts.