Effect of dietary α-linolenic acid on endotoxin-induced production of tumor necrosis factor by peritoneal macrophages in horses

Debra Deem Morris From the Departments of Large Animal Medicine and Physiology and Pharmacology, College of Veterinary Medicine, The University of Georgia, Athens, GA 30602.

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Michelle M. Henry From the Departments of Large Animal Medicine and Physiology and Pharmacology, College of Veterinary Medicine, The University of Georgia, Athens, GA 30602.

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James N. Moore From the Departments of Large Animal Medicine and Physiology and Pharmacology, College of Veterinary Medicine, The University of Georgia, Athens, GA 30602.

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J. Kay Fischer From the Departments of Large Animal Medicine and Physiology and Pharmacology, College of Veterinary Medicine, The University of Georgia, Athens, GA 30602.

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SUMMARY

A study was conducted to determine whether dietary supplements with α-linolenic acid altered the ability of equine peritoneal macrophages to produce tumor necrosis factor (tnf) in response to endotoxin. Peritoneal macrophages were harvested from 6 healthy adult horses before and after the horses were fed a nutritionally balanced ration that contained 8% linseed oil as a source of α-linolenic acid. The macrophages were cultured in media containing no additives (control), endotoxin (0.5 to 50 ng/ml), or the calcium ionophore, A23187. Macrophage supernatants were collected after 6 and 24 hours’ incubation and stored at −70 C. Tumor necrosis factor activity was estimated by a modified in vitro cytotoxicity bioassay, using the murine fibrosarcoma cell line, WEHI 164 clone 13. The tnf activity after 6 and 24 hours’ incubation was greater in culture media of macrophages exposed to endotoxin than in media from control macrophages. For macrophages cultured in media that contained endotoxin, neither the concentration of endotoxin nor incubation time had any effect on tnf activity. Endotoxin-induced macrophage production of tnf, as determined by measurement of tnf activity, was significantly less after horses were fed the α-linolenic acid-rich ration for 8 weeks.

SUMMARY

A study was conducted to determine whether dietary supplements with α-linolenic acid altered the ability of equine peritoneal macrophages to produce tumor necrosis factor (tnf) in response to endotoxin. Peritoneal macrophages were harvested from 6 healthy adult horses before and after the horses were fed a nutritionally balanced ration that contained 8% linseed oil as a source of α-linolenic acid. The macrophages were cultured in media containing no additives (control), endotoxin (0.5 to 50 ng/ml), or the calcium ionophore, A23187. Macrophage supernatants were collected after 6 and 24 hours’ incubation and stored at −70 C. Tumor necrosis factor activity was estimated by a modified in vitro cytotoxicity bioassay, using the murine fibrosarcoma cell line, WEHI 164 clone 13. The tnf activity after 6 and 24 hours’ incubation was greater in culture media of macrophages exposed to endotoxin than in media from control macrophages. For macrophages cultured in media that contained endotoxin, neither the concentration of endotoxin nor incubation time had any effect on tnf activity. Endotoxin-induced macrophage production of tnf, as determined by measurement of tnf activity, was significantly less after horses were fed the α-linolenic acid-rich ration for 8 weeks.

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