Exaggerated liver injury induced by ischemia-reperfusion in spontaneously hypertensive rats.

BACKGROUND: The functions of polymorphonuclear leukocytes (PMNs), which play a critical role in organ damage, are primed in patients with essential hypertension and spontaneously hypertensive rats (SHR). Hepatic ischemia-reperfusion (I/R) injury is shown to be caused and aggravated by the PMNs. We examined whether the hepatic I/R injury was exaggerated in SHR. METHODS: The portal vein and artery were partially occluded for 60 min. Blood samples were obtained to determine the degree of liver damage during 48 h after reperfusion. RESULTS: The increase in serum transaminase concentration and hepatic myeloperoxidase content, which reflects the number of PMNs in liver tissue, in SHR were significantly greater than those of their control rats, Wistar-Kyoto rat (WKY). However, the elevations in hepatic transaminases induced by I/R did not differ between other hypertensive animal models (N-nitro-L-arginine methyl ester [L-NAME]-treated and deoxycorticosterone acetate [DOCA]/salt-treated rats) and their controls. CONCLUSIONS: These results suggest that the elevated PMNs, but not high blood pressure per se, contributes to the exaggerated hepatic I/R injury in SHR.

Comparative study of taste disturbance by losartan and perindopril in healthy volunteers.

The aim of this study was to compare the degree of taste disturbance by losartan, an angiotensin II receptor blocker, with that of perindopril, an angiotensin-converting enzyme inhibitor. Perindopril erbumine (2 mg), losartan potassium (25 mg), or vehicle was given to Japanese volunteers (n = 7) for 14 days in a randomized, placebo-controlled, 3-way crossover design with a 14-day washout period. Gustometry by filter-paper test and electrogustometry were performed before and at the end of each trial. Plasma renin activity (PRA) and serum and salivary zinc concentrations were measured. One subject dropped out because of a perindopril-induced dry cough, but no one claimed a taste disturbance. Detection thresholds of 4 basic tastes (sweet, salty, sour, and bitter) by the paper-disc test and electrogustometry were significantly worsened, and plasma renin activity was elevated by the drugs, whereas the deteriorating effects of 2 drugs did not significantly differ. These drugs did not affect zinc concentrations in plasma and saliva. It was concluded that losartan and perindopril similarly alter taste sensitivity during repeated dosing of the drugs.

Chronopharmacology of morphine in mice.

Dosing-time-dependent changes in the effect and toxicity of morphine were examined in mice housed under alternating 12 h light (07:00 to 19:00 h) and dark (19:00 to 07:00 h) cycles. Morphine (0.5 mg/kg) was injected intraperitoneally (i.p.) in animals to assess its beneficial effect (i.e., protection against the kaolin-induced, bradykinin-mediated, writhing reaction) and its toxicity (i.e., alteration of the hepatic enzymes of aspartate aminotransferase [AST] alanine aminotransferase [ALT], and glutathione [GSH] in separate experiments). The magnitude of the analgesic effect of morphine depended on dosing time, with minimum effect at 02:00 h and maximum effect at 14:00 h. The serum hepatic enzyme levels of AST and ALT increased after dosing morphine (100 mg/kg) at 02:00 and 14:00 h. Time courses of these enzymes did not differ between the two trials. However, hepatic GSH, which is involved in the detoxification of chemical compounds, significantly decreased after i.p. morphine injection at 02:00 but not at 14:00 h. Overall, the results suggest that the analgesic effect of morphine is greater after dosing during the resting than during the activity phase of mice that have been induced with bradykinin-mediated pain. Drug-induced hepatic damage as inferred by GSH alteration, however, may be greater after dosing during the active phase.

Dosing-time-dependent differences in lipopolysaccharide-induced liver injury in rats.

Dosing-time-dependent differences in lipopolysaccharide (LPS)-induced liver injury were examined in rats housed under a 12 h light : dark (LD) cycle. LPS (5 mg/kg) was intravenously injected into different groups of rats at 2, 14, or 20 h after light on (HALO). Elevations in serum liver enzymes after 14 HALO were significantly greater than those after 2 HALO. These parameters were lower in rats given LPS at 20 HALO, compared to 14 HALO. The number of polymorphonuclear cells (PMN) in the liver and the amount of hepatic myeloperoxidase activity, which reflects the number of PMN in liver tissues, was significantly greater in the 14 than in the 2 HALO group. In addition, hepatic interleukin-6 (IL-6) production in the 14 HALO group was enhanced compared to that in the 2 HALO trial. These results suggest that LPS-induced liver injury is greater during the early active than during the early resting period. Dosing-time-dependent variation in the accumulation of PMN in the liver and, potentially, subsequent IL-6 production in liver tissues might be involved in this phenomenon.

Evaluation of chronopharmacodynamics of indomethacin by the kaolin-induced pain model in mice.

We previously showed that the kaolin-induced writhe reaction exhibits 24 h variation with a peak at the end of the resting period (14:00-18:00 h) in mice maintained under light from 07:00 to 19:00 h. In this study, we used this model to evaluate the administration-time-dependent (chronopharmacodynamic) effect of indomethacin. Indomethacin (0.5 mg/kg) was given orally to mice at 02:00, 08:00, 14:00, or 20:00 h, and the suppressive effect on kaolin-induced writhing was determined after each timed dosing. After dosing at 08:00 h, indomethacin remarkably reduced the number of writhes during the critical span of 14:00-18:00 h--the time when writhing reaction was greatest during the 24 h, while the suppressive effect of the medicine after dosing at the other clock times was relatively small. These data suggest the analgesic effect of indomethacin in mice with the kaolin-induced writhing is greater after dosing in the early resting period, which is similar to that reported in patients with nocturnalpain. The kaolin-induced pain mouse model seems to be useful for the chronopharmacodynamic evaluation of analgesic agents.

Inhibition of CYP3A4 by 6',7'-dihydroxybergamottin in human CYP3A4 over-expressed hepG2 cells.

OBJECTIVES: We previously established HepG2-GS-3A4, a cell line from hepatoblastoma with overexpression of human CYP3A4 and glutamine synthetase (GS). We further reported that these cells can be applied for screening inhibitors of CYP3A4 in vitro. The purpose of this study was to determine whether our CYP3A4-overexpresed cell could be applied to evaluate mechanisms of CYP3A4 inhibition by 6',7'-dihydroxybergamottin (DHB), which is one of the major furanocoumarins in grapefruit juice, by using these cells. METHODS: Nifedipine oxidation, activity and protein expression of NADPH-cytochrome reductase (POR) of HepG2-GS-3A4 cell were measured. CO-binding spectrumassay in microsomal fraction of the cells was also evaluated. KEY FINDINGS: DHB and ketoconazole, a well-known inhibitor of CYP3A4, inhibited nifedipine oxidation in a concentration-dependent manner. DHB at a concentration of 3.0 µm, sufficient to inhibit the nifedipine oxidation, decreased POR activity; however, ketoconazole at a concentration of 0.9 µm, sufficient to inhibit the oxidation, did not affect the activity. The expression of POR protein in HepG2-GS-3A4 cells was not changed by either DHB or ketoconazole. The expression of CYP3A4 mRNA and protein was not changed by the addition of DHB or ketoconazole. DHB also reduced the absorption rate at 450 nm in a CO-binding spectrum assay without alteration of the wavelength of maximum absorption. The mean absorption value at 450 nm slightly decreased with ketoconazole; however, the difference was not significant. CONCLUSIONS: We concluded that inhibition of CYP3A4 activity by DHB includes the inhibition of POR activity. HepG2-GS-3A4 might be a good tool to evaluate the mechanisms.

Interaction between grapefruit juice and hypnotic drugs: comparison of triazolam and quazepam.

OBJECTIVE: Grapefruit juice (GFJ) inhibits cytochrome P450 (CYP) 3A4 in the gut wall and increases blood concentrations of CYP3A4 substrates by the enhancement of oral bioavailability. The effects of GFJ on two benzodiazepine hypnotics, triazolam (metabolized by CYP3A4) and quazepam (metabolized by CYP3A4 and CYP2C9), were determined in this study. METHODS: The study consisted of four separate trials in which nine healthy subjects were administered 0.25 mg triazolam or 15 mg quazepam, with or without GFJ. Each trial was performed using an open, randomized, cross-over design with an interval of more than 2 weeks between trials. Blood samples were obtained during the 24-h period immediately following the administration of each dose. Pharmacodynamic effects were determined by the digit symbol substitution test (DSST) and utilizing a visual analog scale. RESULTS: GFJ increased the plasma concentrations of both triazolam and quazepam and of the active metabolite of quazepam, 2-oxoquazepam. The area under the curve (AUC)(0-24) of triazolam significantly increased by 96% (p<0.05). The AUC(0-24) of quazepam (+38%) and 2-oxoquazepam (+28%) also increased; however, these increases were not significantly different from those of triazolam. GFJ deteriorated the performance of the subjects in the DSST after the triazolam dose (-11 digits at 2 h after the dose, p<0.05), but not after the quazepam dose. Triazolam and quazepam produced similar sedative-like effects, none of which were enhanced by GFJ. CONCLUSION: These results suggest that the effects of GFJ on the pharmacodynamics of triazolam are greater than those on quazepam. These GFJ-related different effects are partly explained by the fact that triazolam is presystemically metabolized by CYP3A4, while quazepam is presystemically metabolized by CYP3A4 and CYP2C9.

Subclinical alteration of taste sensitivity induced by candesartan in healthy subjects.

AIMS: There have been case reports of taste disturbance for the angiotensin II receptor blockers losartan and valsartan, but not for candesartan. This study was undertaken to examine whether candesartan causes taste disturbance. METHODS: Candesartan cilexetil (4 mg day(-1)) or vehicle was given to healthy volunteers (n = 8) for 7 days in a randomized, double-blind, placebo-controlled, cross-over design with a 2-week washout period. Clinical gustometry using the filter-paper disc test and electrogustometry were sequentially performed before and at the end of each trial. Serum and salivary zinc concentrations were also measured. RESULTS: Detection thresholds of four basic tastes (sweet, salty, sour and bitter) determined by the paper disc test were significantly (P < 0.05 in all tests) worsened (i.e. score of test increased) after repeated dosing of the drug, although the subjects did not notice such changes. The mean +/- SEM (and 95% CI) scores of the four tastes at just before the seventh dosing of candesartan or vehicle was 3.38 +/- 0.32 (3.02, 3.74) and 2.63 +/- 0.18 (2.18, 3.08) for sweetness, 3.63 +/- 0.38 (4.49, 2.77) and 2.63 +/- 0.26 (3.27, 1.98) for salt, 4.01 +/- 0.42 (3.04, 4.98) and 2.61 +/- 0.32 (3.35, 1.87) for sourness, 4.01 +/- 0.38 (3.22, 4.80) and 2.99 +/- 0.33 (2.24, 3.74) for bitterness, for candesartan and placebo, respectively. Electrogustometry confirmed the candesartan-related taste disturbance. Serum and salivary zinc concentrations were not influenced by candesartan. CONCLUSIONS: These data suggest that candesartan subclinically reduces taste sensitivity after repeated dosing in healthy subjects. Because similar events are reported for losartan and valsartan in case reports, this adverse effect might be a class effect of angiotensin-II receptor blockers (ARBs).