Metabolism of clozapine by cDNA-expressed human cytochrome P450 enzymes

The metabolism of clozapine was studied in vitro using cDNA-expressed human cytochrome P450 (CYP) enzymes 1A2, 3A4, 2C9, 2C19, 2D6, and 2E1. CYP1A2, 3A4, 2C9, 2C19, and 2D6 were able to N-demethylate clozapine. N-Oxide formation was exclusively catalyzed by CYP3A4. CYP2E1 did not metabolize clozapine. With regard to quantitative relationships, CYP1A2, 2C9, 2C19, and 2D6 displayed KM values ranging from 13 to 25 microM, whereas CYP3A4 had a 5-10 times higher KM value. CYP2C19 and 2D6 had the highest Vmax values (149-366 mol/hr/mol CYP). Taking into account the typical relative distribution of amounts of CYP enzymes in the liver, a simulation study suggested that at therapeutic concentrations CYP2C19 and CYP3A4 each accounted for about 35% of the metabolism. At toxic concentrations, the relative importance of CYP3A4 increased.     

Comparative analysis of latrotoxin channels of different conductance in planar lipid bilayers. Evidence for cluster organization

It has been established that channels induced by Latrodectus tredicimguttatus alpha-toxin (LT) in lipid bilayers have a cluster organisation. So far as: (i) the LT-channels had practically identical sizes of its water pores (r = 9.4 +/- 0.6 A) independently on the lipid composition of planar bilayer lipid membrane (BLM) although their conductances might differ from each other more than 10 times (100 mM KCl (pH 7.5)). (ii) affinity of permeable ions to channels had a small variation with distinct group of BLM, although LT-channels conductances varied from 112 +/- 8 pS till 1110 +/- 40 pS for phosphatidylcholine-BLM and from 75 +/- 6 pS till 170 +/- 14 pS for phosphatidylserine-BLM. (iii) Ca/K selectivity was greater in negatively charged membranes but did not also depend on the channel amplitude for the same BLM. Cation-anionic selectivity was identical for all studied channels.     

Dynorphin A(6-12) analogs suppress thermal edema

Dynorphin A (Dyn A) is a 17-residue opioid peptide derived from prodynorphin precursors found in mammalian tissues. Removal of Tyr1 from Dyn A produces a peptide that is more potent than Dyn A in attenuating the acute phase of the inflammatory response, as measured by inhibition of heat-induced edema in the anesthetized rat's paw (exposure to 58 degrees C water for 1 min). Dyn A(2-17), however, no longer interacts with opioid receptors. It was postulated that the non-opioid anti-inflammatory actions of Dyn A(2-17) may reside in Dyn A(6-12); that is, Arg-Arg-Ile-Arg-Pro-Lys-Leu. here we report on the activities of Dyn A(6-12) analogs modified by substitutions on the N terminus, by single N-methyl substitution and by single replacement of residues by alanine. The results indicated that the minimal sequence required for an anti-edema ED50 of <1.0 micromol/kg i.v. was anisoyl-Arg6-Arg7-Xaa8-Arg9-Pro10)-Xaa11-+ ++Xaa12-NH2. A prototype, p-anisoyl-[D-Leu12] Dyn A(6-12)-NH2, with an ED50 of 0.20 micromol/kg i.v. compared to an ED50 of 0.08 micromol/kg i.v. for Dyn A(2-17), was selected for further tests of biological activity. This analog, like Dyn A(2-17), lowered blood pressure in anesthetized rats. In a model of neurogenic inflammation, produced by antidromic stimulation of the vagus in the anesthetized rat, p-anisoyl-[D-Leu12] Dyn A(6-12)-NH2, 0.23 micromol/kg i.v., attenuated the negativity of tracheal tissue interstitial pressure (Pif), which normally develops after nerve stimulation. Modulation of interstitial pressure may be the mechanistic basis for the anti-edema properties of these Dyn A(6-12) analogs.     

The determination of opiates by latex agglutination

A method based on latex agglutination test has been developed for detection of opiates in human urine. Specific reagents were synthesized and conditions of interaction of conjugated latex antigens with specific antibodies to morphine in the presence of an inhibitor were examined. Sensitivity of the method was 100 ng/ml. The developed latex agglutination test for detection of opiates may be used in combination with enzyme immunoassay in practical forensic medicine and narcology.