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Neutrophils which ingest particles (serum-treated zymosan, monosodium urate crystals) or are exposed to calcium ionophore A23187 generate leukotriene B4 (LTB4). Earlier work has shown that cells exposed to colchicine before exposure to monosodium urate crystals produce less LTB4; the formation of 5-HETE is unaffected. To determine whether inhibition by colchicine of LTB4 generation was stimulus-specific and was mediated by microtubule integrity, the effects of colchicine (10 microM, 60 min) on the release of lipoxygenase products from neutrophils exposed to ionophore A23187 (10 microM, 5 min) were examined. In the presence of exogenous arachidonic acid (100 microM, 15 min), colchicine decreased LTB4 to 48% +/- 11.7 of control and 5-HETE to 60.5% +/- 5.7 of control (mean +/- SEM); 15-HETE was also decreased to 61% +/- 10.3 of control. In the absence of exogenous arachidonate, LTB4 was decreased to 22.2% +/- 11.7 of control and 5-HETE to 13% +/- 4.8 of control. Lumicolchicine did not significantly affect formation of 5-HETE or LTB4. However, vinblastine sulfate (20 microM, 60 min), another microtubule-disruptive agent, decreased the formation of both 5-lipoxygenase products. The effects of colchicine and vinblastine were not due to impairment of cell viability because the release of cytoplasmic lactic dehydrogenase was unaffected. Ultrastructural analysis of centriolar microtubules showed that decrements in microtubule numbers of colchicine- and vinblastine-treated cells paralleled decrements in 5-lipoxygenase products. These pharmacologic manipulations suggested that functional microtubules might be required for optimal lipoxygenase activity. Consequently, we prepared neutrophil-derived cytoplasts, devoid of an intact microtubule system. No significant decreases in the 5- or 15-lipoxygenase products were found when cytoplasts were exposed to colchicine in the presence of exogenous arachidonate and A23187. The data show that colchicine inhibits the formation of lipoxygenase products from neutrophils stimulated with A23187, most likely via its effect on microtubules, the integrity of which appears necessary for full expression of 5- and 15-lipoxygenases

Transfusion of donor blood containing predominantly younger red cells with prolonged survival in vivo could significantly reduce the iron overload of patients requiring chronic transfusion. Age-dependent separation of red cells can be obtained by buoyant density centrifugation on isotonic solutions of arabino-galactane. By this technique, rabbit red cells were separated on a single layer of arabino-galactane and the appropriate fraction, after being labeled with (51)Cr, was reinfused into the donor. The survival in vivo was calculated by a mathematical model which corrects for both (51)Cr elution and random loss. There was a significant difference in survival in vivo between the light young red cells and the heavy old red cells. The potential survival in vivo of the 50% lightest red cells was 56 days, compared to 28 days for the heaviest red cells. Arabino-galactane appeared to be devoid of acute toxicity and of strong antigenicity and it did not appear to adhere to the red cell stroma. These data extrapolated to humans indicate that it may be feasible and advantageous to use red cells fractionated by this technique for transfusion. The 50% lightest human red cells can be expected to have a mean survival of 88 days, compared with 60 days for unfractionated blood. Transfusion of young red cells could significantly reduce the iron overload for patients requiring chronic transfusion, by avoiding infusion of the oldest red cells, which contribute equally to iron overload yet offer only transient survival in vivo.