Abstract
The purpose of this study was to evaluate the biological response of sheep to different doses of endotoxin and endotoxin-contaminated enzyme preparations. The enzyme used in this experiment was superoxide dismutase (SOD), as it is currently being used in many different experiments and because several preparations were found to be heavily contaminated with endotoxin.
A group of ewes were injected intravenously with a variety of different treatments. Peripheral blood was used to determine the total number of leukocytes, a differential cell count to find out the numbers of polymorphonucleocytes (PMN) and monocytes (M), and to measure the concentration of 15-ketodihydro-PGF2α. In addition, rectal temperature was recorded. Treatments included saline (control), Pharmacia-Chiron’s Cu/Zn-SOD (r-hSOD, 8 mg/kg), Sigma’s bovine SOD (bSOD, 8 mg/kg), Grünenthal’s bSOD (8 mg/kg), various doses of Salmonella typhimurium endotoxin (1000, 200, 100, 50, 20, 10, 5, and 1 ng/kg), and a mixture of endotoxin (200 ng/kg) plus r-hSOD (8 mg/kg).
Results indicate that sheep react to endotoxin-contaminated SOD preparations with an endotoxemia which is similar to that seen in animals receiving endotoxin alone. This endotoxemia includes, among other things, a rise in rectal temperature, a peak in the PGF2α metabolite, and an increased PMN/M ratio.
Endotoxin administered at doses of 50 to 200 ng/kg also caused the expected signs of endotoxemia. At 1000 ng/kg endotoxin actually led to a decreased rectal temperature. This may be due to a type of endotoxemic shock, resulting in a decrease in peripheral blood circulation.
Low doses of endotoxin (10, 5, and 1 ng/kg) caused a leukocytosis via increases in PMN; no greater changes in rectal temperature or the PGF2α metabolite were noted.
The combination of r-hSOD with 200 ng/kg of endotoxin caused an endotoxemia similar to that caused by 200 ng/kg of endotoxin alone.
In conclusion, if an endotoxin-contaminated SOD-preparation was used to study the efficacy of SOD, there would be a serious risk of interaction by the endotoxins. In such a case it would be impossible to distinguish the effects of the endotoxin from those of the preparation itself. It is therefore important that researchers are alert to the problem of endotoxin contamination.
Keywords: prostaglandin, leukocytes
Sammanfattning
Syftet med denna studie är att bedöma det biologiska svaret hos får till olika doser av endotoxin och några endotoxin-kontaminerade enzympreparationer. Enzymet som användes i detta försök var superoxid-dismutas (SOD), eftersom det studeras i många olika försök och några preparationer upptäcktes vara svårt kontaminerade av endotoxiner. En grupp av tackor injicerades intravenöst med några olika behandlingar. Perifert blod användes för att räkna det totala antalet leukocyter, göra en differentialräkning för att skilja polymorfonukleocyter (PMN) från monocyter (M), och mäta koncentrationen av 15-ketodihydro-PGF2α•Vidare, uppmättes rektaltemperaturen. Behandlingar inkluderede koksalt (kontroll), Pharmacia-Chiron’s Cu/Zn-SOD (r-hSOD, 8 mg/kg), Sigma’s bovina SOD (bSOD, 8 mg/kg), Grünenthal’s bSOD (8 mg/kg), olika doser av Salmonella typhimurium endotoxin (1000, 200, 100, 50, 20, 10, 5, och 1 ng/kg), och en blandning av endotoxin (200 ng/kg) plus r-hSOD (8 mg/kg).
Resultaten visar att får reagerar mot endotoxinkontaminerade SOD preparationer med en endotoxemi som liknar den som finns hos djur som har fått rent endotoxin. Denna endotoxemi inkluderar, bl. a., en ökning i rektaltemperatur, en topp i PGF2α metaboliten, och en ökning i PMN/M kvot.
Endotoxin administrerat i doser melian 50 till 200 ng/kg framkallade också den förväntade bilden på endotoxemi. Emellertid, ledde en dos av 1000 ng/kg endotoxin till en sänkning av rektaltemperaturen. Detta kan bero på att djuren har kommit i ett endotoxemisk chocktillstånd, och därför har den perifera blodcirkulation minskat.
Lägre doser av endotoxin (10, 5, och 1 ng/kg) orsakar en leukocytos på grund av en ökning i PMN; det var ingen markant förändring i rektaltemperatur eller i 15-ketodihydro-PGF2α koncentrationen. Endotoxemi som framkallades av blandningen av r-hSOD med 200 ng/kg endotoxin liknade den som orsakades av samma dos av endast endotoxin.
Sammanfattningsvis, om en endotoxin-kontaminerad enzympreparation användes i en farmakologisk studie skulle det sannolikt producera missvisande resultat. Det skulle vara svårt att skilja effekterna av endotoxinet från de av preparationen själv. Därför är det viktigt att forskarna är medvetna om möjligheten att preparationerna som användes i försök kan vara kontaminerad av endotoxiner.
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