No abstract

The cytotoxic effects of latanoprost, travoprost, and bimatoprost were dependent on the BAC concentration in their formulations. BACmix was cytotoxic at the concentrations above those corresponding to 0.001% BAC in ophthalmic medications. PF tafluprost was the least toxic of the drugs tested. Within studied BAC homologs, those with longer alkyl chain and higher lipophility penetrated effectively into rabbit external ocular tissues.

The effects of daily cocaine administration for up to 14 days were studied in terms of hepatic morphology and the expression of cytochrome P450 (CYP) enzymes in the mouse liver. Daily intraperitoneal doses of 60 mg/kg of cocaine for 3 days induced severe hepatocellular necrosis in the pericentral zone and decreased activities of CYP1A2, CYP2A4/5, and CYP2Cx. The microsomal CYP2B10 protein content was increased by about 2.5-fold, but 2B10-dependent 7-pentoxyresorufin O-dealkylase (PROD) activity was barely detectable. Five or seven daily cocaine doses caused prominent pericentral inflammation and a significant (up to 14-fold) increase in the microsomal protein content and PROD activity. An increase in microsomal CYP3A was also evident, but CYP2A5 and CYP1A2 still remained at a low level. Immunohistochemical examination showed that the relative induction of CYP2B10 and CYP3A after treatment with cocaine was strongest in perivenous hepatocytes. Immunoinhibition experiments showed that CYP2B10 accounted for catalysis of only 15% to 20% of the enhanced microsomal cocaine N-demethylase (CNDM) activity, which correlated well with immunoreactive 3A protein, and could be blocked 70% to 90% by triacetyloleandomycin. After 10 or 14 daily doses of cocaine, regenerative changes with hepatocyte ballooning were observed, coinciding with increases in CYP1A2, CYP2A4/5, and CYP3A. These results suggest the following: (1) cocaine enhances its own cytochrome P450-dependent metabolism; (2) increased production of norcocaine in microsomes is catalyzed mainly by CYP3A enzyme(s), whereas 2B10, although markedly increased by cocaine treatment, has only a minor role in cocaine hepatotoxicity; and (3) despite increased microsomal CNDM activity, cocaine-induced liver injury is reversible in mice.

Background: Some studies have shown that benzalkonium chloride (BAK), a preservative used in antiglaucoma medications, can increase corneal permeability by acting as a penetration enhancer. Tafluprost is a new prostaglandin F_2α analog in clinical use for the treatment of ocular hypertension and glaucoma. Methods: This study evaluated the corneal penetration of preservative-free tafluprost 0.0015% eye drops and tafluprost 0.0015% eye drops preserved with 0.01% BAK into the aqueous humor of rabbits. Results: After the administration of a single topical dose (30 μl), the maximum concentrations at 45 min of tafluprost acid in aqueous humor were 4.50 ng/ml for preservative-free tafluprost and 3.99 ng/ml for preserved tafluprost. The area under the concentration-time curves from 45 min to 3 h was 5.14 ng h/ml for the preservative-free formulation and 4.54 ng h/ml for the preserved formulation. Conclusions: These data indicate that BAK does not affect the corneal penetration of tafluprost into the rabbit aqueous humor.

Acute effects of a single intraperitoneal dose of allyl alcohol (AA, 64 mg/kg), dimethylnitrosamine (DMNA, 30 mg/kg), hexachlorobutadiene (HCBD, 50 mg/kg), carbon tetrachloride (CCl4, 24 mg/kg), cocaine (60 mg/kg) and pyrazole (300 mg/kg) on the hepatic histology and monooxygenases in DBA/2 and C57Bl/6 strains of mice were investigated. All substances caused histologically verified injury to the liver, which varied in appearance and severity depending on the compound and the mouse strain. Responses of P450-catalyzed reactions were highly dependent on the toxin and varied between different monooxygenase (MO) reactions and two mouse strains. In DBA/2 strain, coumarin 7-hydroxylase (COH) activity was increased from 3- to 5-fold by pyrazole, cocaine, HCBD and CCl4. With respect to P450 content and other MO activities, no changes or even decreases were generally observed. Some exceptions to this rule were found: HCBD significantly increased T15 alpha OH, PROD and EROD activities in C57Bl/6 mice, whereas cocaine caused a significant stimulation of T15 alpha OH and PROD in DBA/2 mice, It is concluded that i) different hepatoxins cause different types of liver injury and responses of the monooxygenase complex ("hepatotoxinspecific finger prints"), ii) although DBA/2 and C57Bl/6 mice responded rather similarly to hepatotoxins, also with respect to P450 content and most MO activities, they displayed a profound difference in the behaviour of COH activity, and iii) within the P450 superfamily, the regulation of COH activity seems to be rather unique, also when compared to its structurally close enzyme, testosterone 15 alpha-hydroxylase.

No abstract

Cocaine is hepatotoxic in several species, including man. A high dose of cocaine produces metabolism-dependent, mainly pericentral, liver damage. At 24 h after a single dose of cocaine, mouse hepatic P450 content decreases but CYP2A activities; coumarin 7-hydroxylase and testosterone 15 alpha-hydroxylase increase concomitant with prominent diffuse cell necrosis. Repeated administration of cocaine for up to 5 days decreases CYP1A1/2, 2A4/5, 2Cx, and 2E1 related enzymatic activities. However, after five doses of cocaine, CYP2B10 increases in conjunction with the healing process. In the acute phase, the increased CYP2A activities do not participate in cocaine bioactivation. CYP3A enzymes are principally responsible for the cocaine N-demethylation in human and mouse liver microsomes. The hepatic metabolic CYP enzyme profile will change during prolonged cocaine intake, this being accompanied by altered cell morphology. Possible connections to cocaine toxicity in man are discussed.

The first step in the oxidative metabolism of cocaine is N-demethylation to norcocaine, which is further N-hydroxylated to more toxic N-hydroxynorcocaine. In this study we examined the kinetics of norcocaine N-hydroxylation mediated by cytochrome P450 (CYP) in mouse and human liver microsomes. N-hydroxynorcocaine was identified by analytical HPLC-MS after incubation of norcocaine with mouse liver microsomes in the presence of NADPH. In mouse liver microsomes, there was no apparent difference in Km values for norcocaine N-hydroxylation between male and female microsomes, while the Vmax rate was approximately two times higher in female than in male microsomes (34+/-10 v. 16+/-4 pmol/min per mg protein). The Km value for norcocaine N-hydroxylation in human liver microsomes was approximately three times higher than that observed in comparable incubations using mouse liver microsomes, whereas the Vmax rate was ten times lower. Both cocaine and norcocaine induced type I difference spectra upon interaction with CYP in mouse liver microsomes. In contrast, in human microsomes both type I and type II spectra were recorded. In the 0.01 to 1 mM concentration range, cocaine and norcocaine inhibited mouse microsomal testosterone 6alpha-, 7alpha- and 16alpha-hydroxylation reactions by 20% to 30%. Testosterone 6beta- and 15alpha-hydroxylations were blocked by 60% and 50%, respectively, by 1 mM norcocaine, while only 40% inhibition was obtained with 1 mM cocaine. Coumarin 7-hydroxylation and pentoxyresorufin O-deethylation were inhibited by 50% by 1 and 0.4 mM norcocaine, respectively. In contrast, 10 and 2 mM cocaine, respectively, were needed to obtain the same degrees of inhibition. In human liver microsomes, 1 mM norcocaine and cocaine blocked testosterone 6beta-hydroxylase by 60% and 40%, respectively. Coumarin 7-hydroxylation was inhibited by only 30% by norcocaine (5.4 mM) and cocaine (10 mM). Norcocaine N-hydroxylation in mouse and human liver microsomes was blocked by 30% and 60%, respectively, by alpha-naphthoflavone (0.1 mM). The reaction was inhibited by 30-40% by metyrapone, cimetidine and gestodene at a concentration of 1 mM in mouse microsomes, while in human microsomes, 70% inhibition was obtained with 1 mM metyrapone and cimetidine. Taken together, these results indicate that (1) norcocaine N-hydroxylation is at least partly a CYP-mediated reaction, (2) the rate of reaction is considerably lower in human liver microsomes than in mouse liver microsomes and (3) several CYP subfamilies including 1A, 2A, 3A and possibly 2B may contribute to the formation of N-hydroxynorcocaine.