Quantitative analysis of endoplasmic reticulum and cytochrome P-450 in hepatocytes from rats injected with methylcholanthrene.
To examine whether the smooth endoplasmic reticulum (SER) proliferates in hepatocytes from animals treated with methylcholanthrene (MC) frequently used as an inducer for the enzymes of the microsomal mono-oxygenase system, we estimated the area of (smooth and rough) ER per unit cytoplasmic volume by morphometry in periportal, midzonal and perivenular hepatocytes from rats injected with 25 mg/kg MC once a day for 3 days. In addition, immunostaining intensity of major MC-inducible cytochrome P-450 (P-450) forms (1A1/1A2) and total P-450 content in the cytoplasm of hepatocytes in the three zones were measured by microphotometry to ascertain whether P-450 is sufficiently induced in each sublobular zone by the administration. In spite of significant increase in the staining intensity of P-450 1A1/1A2 and amount of total P-450, the proliferation of SER (and RER) did not occur in the three-zone hepatocytes from rats injected with MC. In perivenular hepatocytes, constitutive forms of P-450 other than 1A1/1A2 decreased (to 10%) instead of marked increase in P-450 1A1/1A2 (about 20 times), while the constitutive forms decreased to 50% in midzonal hepatocytes and remained unchanged in periportal hepatocytes after MC administration. In addition, the present results show divergence between biochemical and immumohistochemical results previously reported on MC-inducible P-450 after MC administration to be due primarily to a curvilinear relationship between content and intensity.
Tanaka
T
T
Department of Anatomy, Kansai Medical University, Osaka, Japan.
Watanabe
J
J
Asaka
Y
Y
Ogawa
R
R
Kanamura
S
S
D000818:Animals; D019363:Cytochrome P-450 CYP1A1 / Q000032:analysis; D019388:Cytochrome P-450 CYP1A2 / Q000032:analysis; D003577:Cytochrome P-450 Enzyme System / Q000032:analysis*; D018870:Endoplasmic Reticulum, Rough / Q000187:drug effects*; D018871:Endoplasmic Reticulum, Smooth / Q000187:drug effects*; D007091:Image Processing, Computer-Assisted; D007124:Immunoenzyme Techniques; D008099:Liver / Q000166:cytology* / Q000201:enzymology; D008297:Male; D008748:Methylcholanthrene / Q000494:pharmacology*; D008862:Microsomes, Liver / Q000737:chemistry; D051381:Rats; D017207:Rats, Sprague-Dawley
D008748:Methylcholanthrene; D003577:Cytochrome P-450 Enzyme System; D019363:Cytochrome P-450 CYP1A1; D019388:Cytochrome P-450 CYP1A2