The effect of CYP2C19 genotype on the time course of platelet aggregation inhibition after clopidogrel administration.

We evaluated the effect of CYP2C19 genotype over time on the antiplatelet response of clopidogrel in healthy subjects. Seventy subjects enrolled for a pharmacodynamic study and 22 subjects for a pharmacokinetic and pharmacodynamic study took 300 mg clopidogrel on the first day and 75 mg once daily for six consecutive days. The subjects with CYP2C19 poor metabolizers (PM, N = 22) and intermediate metabolizers (IM, N = 37) had significantly delayed time to inhibition of platelet aggregation (IPA) compared with CYP2C19 extensive metabolizers (EM, N = 33) (12 vs. 9 vs. 2 hours as median Tmax , P < .05) after a 300 mg of clopidogrel. During maintenance doses of clopidogrel, IPA values of only CYP2C19 PM subjects were gradually decreased from 30.0 ± 21.9% on day 2 to 23.7 ± 16.6% on day 8 (P > .05 for time effect; P < .05 for time and genotype interaction effect). CYP2C19 PM had decreased Cmax and AUC of thiol metabolite compared with CYP2C19 EM (0.42- and 0.37-fold on day 1, P < .01; 0.39- and 0.34-fold on day 7, P < .01, respectively). Delayed time to reach maximal IPA as well as decreased IPA may influence the increased risk of the acute cardiac events in CYP2C19 PM and IM.

The effect of methanol on the structural parameters of neuronal membrane lipid bilayers.

The structures of the intact synaptosomal plasma membrane vesicles (SPMVs) isolated from bovine cerebral cortexs, and the outer and the inner monolayer separately, were evaluated with 1,6-diphenyl-1,3,5-hexatriene (DPH) and 1,3-di(1-pyrenyl)propane (Py-3-Py) as fluorescent reporters and trinitrophenyl groups as quenching agents. The methanol increased bulk rotational and lateral mobilities of SPMVs lipid bilayers. The methanol increased the rotational and lateral mobilities of the outer monolayers more than of the inner monolayers. n-(9-Anthroyloxy)stearic acid (n-AS) were used to evaluate the effect of the methanol on the rotational mobility at the 16, 12, 9, 6, and 2 position of aliphatic chains present in phospholipids of the SPMVs outer monolayers. The methanol decreased the anisotropy of the 16-(9-anthroyloxy)palmitic acid (16-AP), 12-(9-anthroyloxy)stearic acid (12-AS), 9-(9-anthroyloxy)stearic acid (9-AS), and 6-(9-anthroyloxy)stearic acid (6-AS) in the SPMVs outer monolayer but it increased the anisotropy of 2-(9-anthroyloxy)stearic acid (2-AS) in the monolayers. The magnitude of the increased rotational mobility by the methanol was in the order at the position of 16, 12, 9, and 6 of aliphatic chains in phospholipids of the outer monolayers. Furthermore, the methanol increased annular lipid fluidity and also caused membrane proteins to cluster. The important finding is that was far greater increase by methanol in annular lipid fluidity than increase in lateral and rotational mobilities by the methanol. Methanol alters the stereo or dynamics of the proteins in the lipid bilayers by combining with lipids, especially with the annular lipids. In conclusion, the present data suggest that methanol, in additions to its direct interaction with proteins, concurrently interacts with membrane lipids, fluidizing the membrane, and thus inducing conformational changes of proteins known to be intimately associated with membranes lipids.

Aggregation behaviors and their pH sensitivity of cholesterol-conjugated proteinoids composed of glutamic acid and aspartic acid matrix.

Cholesterol-conjugated proteinoids and their aggregation behaviors were investigated with model proteinoid systems. Model proteinoids of molecular weights in the range of 4000 to 6000 were synthesized by anhydrous thermal condensation forming a matrix with glutamic acid and aspartic acid and of naturally occurring amino acids. Nuclear magnetic resonance and Fourier transform infrared spectra suggested that cholesterol was conjugated to carboxyl group-forming pendants. Native water-soluble proteinoids can form microspheres in acidified or heated conditions, but the cholesterol-conjugated proteinoids were found to form aggregates in water, regardless of the temperature or pH of the solutions. The hydrophobic pendant moieties come to a compact association in core, whereas the hydrophilic chains provide a shield layer.