EFFECT OF INTRAVENOUS ADMINISTRATION OF HYDROXYETHYL-STARCH-DEFEROXAMINE ON OXYGEN-DERIVED FREE-RADICAL GENERATION IN CANCELLOUS BONE SPECIMENS OBTAINED FROM DOGS

The ability of IV administered hydroxyethylstarch-deferoxamine to atte nuate radical production in freshly procured cancellous bone specimens was investigated, using spin-trapping and electron spin resonance (ES R) techniques. A core cancellous bone specimen 10 mm long and 5.6 mm i n diameter was obtained, using aseptic technique, from the proximal po rtion of the humerus of 30 adult mixed-breed dogs. After procurement o f the initial bone specimen, 10 dogs received a 10% solution of hydrox yethyl-starch-deferoxamine in 0.9% NaCl (50 mg/kg of body weight, IV), 10 dogs received an equivalent volume (5 ml/kg, IV) of a 10% solution of hydroxyethyl-starch in 0.9% NaCl and 10 dogs received 0.9% saline solution (5 ml/kg, IV). A second core cancellous bone specimen was obt ained from the contralateral humerus of each dog 45 minutes after trea tment. All specimens were individually incubated in the spin trap alph a-phenyl-N-tert-butylnitrone in Eagle's minimum essential medium, at 2 6 C for 45 minutes, then were frozen at -20 C until they were prepared for analysis by ESR spectroscopy. Each specimen was thawed, homogeniz ed, and extracted in a low-dielectric organic solvent prior to obtaini ng an ESR spectrum, which was analyzed for hyperfine splitting constan ts for radical identification. Each first-derivative spectrum was digi tally double-integrated to obtain an area; these areas were used to co mpare intensities of the spin adducts. Difference in the area obtained before and after treatment: for each dog was expressed as a ratio of: that dog's pretreatment area ([pretreatment - posttreatment]/pretreat ment). The calculated ratios for saline-, hydroxyethyl-starch-, and hy droxyethyl-starch-deferoxamine-treated dogs were compared, using a Kru skal-Wallis (KW) nonparametric test for multiple comparisons of ranked data. Significance was determined at P less than or equal to 0.05. Ad hoc comparisons were performed, using the KW procedure for individual comparisons, with alpha set at 0.05. The mean +/- SD and median ratio for each of the treatment groups were: saline-treated dogs, 0.005 +/- 0.40 and 0.045; hydroxyethyl-starch-treated dogs, -0.063 +/- 0.27 and -0.025; hydroxyethyl-starch-deferoxamine-treated dogs, 0.261 +/- 0.27 8 and 0.335, respectively. There was a significant (P < 0.01, KW) diff erence in the ratios between treatment groups. Ratios for hydroxyethyl -starch-deferoxamine-treated dogs were significantly (P < 0.05, KW) hi gher than that for hydroxyethyl-starch-treated dogs but not for saline -treated dogs. The ratios for saline- and hydroxyethyl-starch-treated dogs were not significantly different. We could not associate signific ant attenuation of radical generation in freshly harvested core cancel lous bone specimens with IV administration of hydroxyethyl-starch-defe roxamine. The potential for unconjugated hydroxyethyl-starch to functi on as an oxidant must considered.