The covalent binding of genistein to the non-prosthetic-heme-moiety of bovine lactoperoxidase leads to enzymatic inactivation / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>Genistein, a major soy isoflavone metabolite (SIF), inactivates oxidation activity of bovine lactoperoxidase (LPO). Modification of the heme moiety of LPO by nitrogen-containing compounds has been shown to inactivate LPO. In contrast, SIF mediated inactivation of LPO does not involve a heme modification and the mechanism of SIF inhibition is poorly understood.</p><p><b>METHODS</b>After inactivation of LPO by genistein in the presence of H(2)O(2), trypsin-digested LPO peptide fragments were collected and analyzed by MALDI-TOF-MS to characterize the chemical binding of genistein(s) to LPO.</p><p><b>RESULTS</b>The heme moiety of LPO was not modified by genistein. A covalent binding study showed that (3)H-genistein bound to LPO with a ratio of ∼12 to 1. After HPLC analysis and peak collection, trypsin-digested peptide fragments were analyzed by MALDI-TOF-MS. The 3H-genistein co-eluted peptide fragments (RT=24 min) were putatively identified as 199IVGYLDEEGVLDQNR214 with two bound genistein molecules or a genistein dimer (2 259 Da), 486TPDNIDIWIGGNAEPMVER504 with two bound genistein molecules or a genistein dimer (2 663 Da), and 161ARWLPAEYEDGLALPFGWTQR182 with three bound genistein molecules or a genistein trimer (3 060 Da). The fragment with a mass of 1 792 Da (RT=36 min) was identified as 132CDENSPYR139 with three genistein molecules or a genistein trimer.</p><p><b>CONCLUSIONS</b>The results suggest that LPO was inactivated by irreversible covalent binding of genistein or genistein polymers to particular peptide fragments constituting regions of the outward domain. No genistein interaction with the prosthetic heme moiety of LPO was observed.</p>

Metabolism of terephthalic acid and its effects on CYP4B1 induction / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To investgate the metabolism of terephthalic acid (TPA) in rats and its mechanism. Methods Metabolism was evaluated by incubating sodium terephthalate (NaTPA) with rat normal liver microsomes, or with microsomes pretreated by phenobarbital sodium, or with 3-methycholanthrene, or with diet control following a NADPH-generating system. The determination was performed by high performance liquid chromatography (HPLC), and the mutagenic activation was analyzed by umu tester strain Salmonella typhimurium NM2009. Expression of CYP4B1 mRNA was detected by RT-PCR. Results The amount of NaTPA (12.5-200 micromol x L(-1)) detected by HPLC did not decrease in microsomes induced by NADPH-generating system. Incubation of TPA (0.025-0.1 mmol x L(-1)) with induced or noninduced liver microsomes in an NM2009 umu response system did not show any mutagenic activation. TPA exposure increased the expression of CYP4B 1 mRNA in rat liver, kidney, and bladder.</p><p><b>CONCLUSION</b>Lack of metabolism of TPA in liver and negative genotoxic data from NM2009 study are consistent with other previous short-term tests, suggesting that the carcinogenesis in TPA feeding animals is not directly interfered with TPA itself and/or its metabolites.</p>

Fenvalerate-induced alterations in calcium homeostasis in rat ovary / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To observe the effects of fenvalerate on calcium homeostasis in rat ovary.</p><p><b>METHODS</b>Female Sprague-Dawley rats were orally given fenvalerate at daily doses of 0.00, 1.91, 9.55, and 31.80 mg/kg for four weeks. The ovary ultrastucture was observed by electron microscopy. Serum free calcium concentration was measured by atomic absorption spectrophotometry. The activities of phosphorylase a in rat ovary were evaluated by the chromatometry. The total content of calmodulin in ovary was estimated by ELISA at each stage of estrous cycle. Radioimmunoassay (RIA) was used to evaluate the level of serum progesterone.</p><p><b>RESULTS</b>Histopathologically, damages of ovarian corpus luteum cells were observed. An increase in serum free calcium concentration was observed in rats treated with 31.80 mg/kg fenvalerate. The activities of phosphorylase a enhanced in all treated groups, and fenvalerate increased the total content of calmodulin significantly in estrus period. Serum progesterone levels declined in fenvalerate exposed rats in diestrus.</p><p><b>CONCLUSION</b>Fenvalerate interferes with calcium homeostasis in rat ovary. Also, the inhibitory effects of fenvalerate on serum progesterone levels may be mediated partly through calcium signals.</p>

Effects of terephthalic acid on rat lipid metabolism / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To study the effect of terephthalic acid (TPA) on lipid metabolism in Sprague-Dawley (SD) rats.</p><p><b>METHODS</b>Five groups of SD rats that ingested 0%, 0.04%, 0.2%, 1%, and 5% TPA, respectively, were included in a 90-day subchronic feeding study. Effects of TPA on levels of serum protein, total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL), total antioxidative capability (T-AOC), superoxide dismutase (SOD) and malondialdehyde (MDA) were observed. Urine samples were collected and analyzed for concentration of ion.</p><p><b>RESULTS</b>TPA decreased the level of serum T-AOC in a dose dependent manner. The contents of serum and bladder MDA significantly decreased in 1% and 5% TPA ingestion groups. Serum CuZn superoxide dismutase (CuZnSOD) lowered in groups of 0.2%, 1%, and 5% TPA. TPA subchronic feeding had no significant influences on serum TC, LDL or HDL, but increased serum TG, TP and ALB after administration of 0.04% and/or 0.2% TPA. Concentrations of urinary Ca2+, Mg2+, Na+, and K+ were elevated in 1% and 5% TPA groups.</p><p><b>CONCLUSION</b>Antioxidative potential decreased after TPA exposure. MDA increase in serum and bladder tissues was one of the most important reactions in rats which could protect themselves against TPA impairment. The decrease of serum CuZnSOD was related to the excretion of Zn2+.</p>

Effects of mono(2-ethylhexyl) phthalate on testosterone biosynthesis in leydig cells cultured from the rat testis / 中华男科学杂志

<p><b>OBJECTIVE</b>To investigate the effects of mono(2-ethylhexyl) phthalate(MEHP), the primary metabolite of di(2-ethylhexyl) phthalate (DEHP), on testosterone biosynthesis in Leydig cells cultured from the Sprague Dawley rat testis.</p><p><b>METHODS</b>Based on the primary Leydig cell culture model, MEHP exposure groups involved control (0 micromol/L), 62.5, 125, 250, 500 and 1000 micromol/L. We observed mitochondria activity with the MTT method, measured the testosterone level with RIA and determined steroidogenesis acute regulatory protein (StAR) mRNA expression with RT-PCR.</p><p><b>RESULTS</b>After Leydig cells were exposed to MEHP for 24 hours, the activity of mitochondria enhanced evidently at 250 micromol/L and then declined markedly at 1000 micromol/L compared with the control group (P < 0.01). The testosterone level showed an increasing tendency in both basal and hCG-stimulated states with statistical significance at 250 and 500 micromol/L compared with the control group (P < 0.01). However, the expression of StAR mRNA appeared unchanged at 62.5, 125 or 250 micromol/L, but exhibited a decreasing tendency at 500 and 1000 micromol/L (P < 0.01).</p><p><b>CONCLUSION</b>ME- HP directly affected the activity of mitochondria and testosterone biosynthesis of the Leydig cells in vitro. StAR, the regulator of cholesterol transport into mitochondria, might not be responsible for the increase of testosterone biosynthesis induced by MEHP.</p>