The effects of prochloraz on some microsomal parameters in rat liver.

Abstract

The antifungal agent prochloraz [l-n-propyl-N(2,4,6-trichlorophenoxy ethylcarbamoyl)-imidazole] induces cytochrome P-450 in the liver of vertebrates and interacts with lipid metabolism (Riviere et al. 1984; Laignelet et al. 1986). A study was undertaken to detect changes in lipid composition and fluidity of microsomal membranes. Sprague-Dawley rats (180-190g) were injected i.p. with either 600 Ixmol/kg prochloraz (95% pure; Schering Co.) in corn oil or with corn oil only, 3 days before sacrifice. In the liver homogenates vitamin A was measured (Olson 1979). The following assays were carried out with the microsomal suspensions: benzo(a)pyrene monooxygenase activity (BaPMO) (Depierre et al. 1975), epoxide hydrolase activity (EH) (Oesch et al. 1971), microsomal protein content (Lowry et al. 1951) and cytochrome P-450 content (Omura and Sato 1964). Microsomal lipids were extracted (Bligh and Dyer 1959) and quantitatively determined (Canal et al. 1973); cholesterol content was also measured (Boehringer Mannheim standard kit). Individual phospholipids were separated by two-dimensional TLC (Wolff et al. 1984) and total lipid phosphorus as well as individual phospholipids were thus determined (Ames 1966). Fatty acids were derivatized to their methyl esters (Morrison and Smith 1964) and analysed by GLC. Microsomal fluidity was studied at 37~ by fluorescence depolarization measurement of diphenyl hexatriene (DPH) according to Schinitzki and Barenholdz (1978). The results are summarized in Table 1 and all the differences indicated below are significant (at p < 0.01 level; t test calculation). Prochloraz significantly increased liver weight (+ 27%) and decreased the vitamin A liver burden (-17%). In treated animals the microsomal protein content of whole liver was significantly increased (nearly 40%). In microsomes of treated animals cytochrome P-450 content and BaPMO activity were significantly increased (+21% and + 121%, respectively), although EH activity was not altered. Prochloraz did not change the total lipid and phospholipid contents in microsomal membranes. However, the cholesterol level in these membranes and thus the phospholipid/cholesterol molar ratio were decreased ( -22% and -20%, respectively). Consequently, the microviscosity, evaluated in terms of fluorescence with the probe DPH, was significantly decreased ( 12%). It was reported that prochloraz inhibited lanosterol 14-demethylation (a cytochrome P-450 dependent reaction) in fungi (Schwinn 1983) and increased lanosterol liver content in Japanese quails (Riviere et al. 1984). More-