Metabolism, disposition and Escherichia coli-induced production of cysteinyl leukotrienes and other eicosanoids in the anesthetized and endotoxemic dog

Cynthia Ann Pfeifer, Purdue University

Abstract

Cysteinyl leukotrienes (LTs) and other eicosanoids are believed to play pivotal roles in endotoxemia pathophysiology. Methods were developed and validated to determine in vivo and in vitro metabolism, disposition and endogenous production of cysteinyl LTs and other eicosanoids in control and endotoxin-treated dogs. The metabolism and disposition of leukotrienes were studied following an IV infusion of tritiated leukotriene C$\sb4$, ($\sp3$H) -LTC$\sb4$, in anesthetized control and endotoxin-treated dogs. Cumulative ($\sp3$H) -LTC$\sb4$ metabolic patterns in bile and urine over time were determined by RP-HPLC separation and fraction collection. Three primary metabolites, ($\sp3$H) -LTD$\sb4$, ($\sp3$H) -LTE$\sb4$ and a polar metabolite, (0.15-0.19)LT, accounted for most of the total bile and urine radioactivity in both dog groups. However, no N-acetyl LTE$\sb4$ was detected in bile or urine for either group. Pharmacokinetic analysis (two-compartment) along with the maintained higher plasma levels of tritiated leukotrienes, ($\sp3$H) -LTs, in endotoxin-treated dogs suggests that endotoxin caused a decreased body clearance and less peripheral tissue penetration of ($\sp3$H) -LTs. The endogenous production of cysteinyl LTs in response to E. coli infusion was measured by sequential RP-HPLC separation and radioimmunoassay quantitation. Endotoxin-treated dogs showed only an increase of biliary leukotriene D$\sb4$(LTD$\sb4$) from baseline levels when compared to levels found in control dogs after 60 minutes. Collectively, these results indicate that the metabolism of LTC$\sb4$ to LTD$\sb4$ and LTE$\sb4$, but not N-acetyl LTE$\sb4$, in dogs was similar to that reported for man, pig and monkey but dissimilar to rat. Endotoxin did not affect the types or relative amounts of the major LT metabolites found in bile or urine, but altered the disposition of ($\sp3$H) -LTs by decreasing clearance and distribution. Endotoxin also induced the production of cysteinyl LTs and PGI$\sb2$, TXA$\sb2$ and PGE$\sb2$ in the dog.

Degree

Ph.D.

Advisors

Bottoms, Purdue University.

Subject Area

Anatomy & physiology|Animals|Veterinary services|Pharmacology

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