ISSN:
1573-4919
Keywords:
pyridine
;
induction
;
culture rat liver hepatocytes
;
CYP1A1
;
CYP1A2
;
CYP2E1
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
Notes:
Abstract In vivo administration of pyridine has been shown to increase theactivity and content of several forms of cytochrome P450 by transcriptionaland posttranscriptional mechanisms. The effect of pyridine on CYP1A andCYP2E1 isozymes was studied in a rat hepatocyte culture model. Hepatocyteswere isolated from non-induced rats and seeded onto matrigel-coated dishesand incubated in William's medium E containing 10% fetal calf serum,hormones, and essential metals. Cultures were treated with 0, 10 or 25 mMpyridine for 1-3 days and microsomes were isolated to determine catalyticactivity and for immunoblot analysis, and total RNA was isolated for mRNAdeterminations. CYP2E1 content, CYP2E1 mRNA, and CYP2E1 catalyzed oxidationof p-nitrophenol declined during culture to values of 3, 30 and 19%that of initial, non-cultured controls by day 3 of culture. Pyridineprevented this decline of CYP2E1 protein and activity such that60-80% original activity remained after 3 days of culture in thepresence of 25 mM pyridine. However, pyridine did not prevent the fall inCYP2E1 mRNA levels, nor did pyridine increase the content or activity ofCYP2E1 above initial values of microsomes from freshly isolated hepatocytes.Pyridine increased the content of CYP1A2 and the oxidation ofethoxyresorufin 2-4 fold compared to cultures incubated without pyridineover the 3 day culture period. CYP1A1 levels, which rapidly declined, wereinduced and maintained in the presence of pyridine. Pyridine increased CYP1Acontent and activity 2-3 fold over initial values of freshly isolatedhepatocytes. These increases were associated with corresponding increases inCYP1A mRNA levels. CYP1A2, but not CYP1A1, mRNA levels increased in thecultures incubated in the absence of pyridine. These results indicate thatpyridine has different effects on CYP1A1 and CYP2E1 in this hepatocyteculture model. Pyridine appears to modulate CYP2E1 levels byposttranscriptional mechanisms as CYP2E1 activity and content weremaintained in the presence of pyridine under conditions in which CYP2E1 mRNAlevels declined. These mechanisms may involve increased translationalefficiency of existing CYP2E1 mRNA or stabilization of CYP2E1 proteinagainst degradation. Pyridine increased CYP1A1 and CYP1A2 content, activityand mRNA levels, either inducing CYP1A transcription or stabilizing CYP1AmRNA. Hepatocyte cultures may be a useful model to study the interaction ofpyridine with P450 isozymes and their associated drug-mediated toxicity.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1006831811622
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