Regulation of Intermittent Hypoxia on Brain Dopamine in Amphetaminized Rats.

We investigated intermittent hypoxia (IH) on dopamine (DA) release in rat brain treated with or without amphetamine (AMPH). Rats were divided into four groups including normoxia, IH, AMPH, and AMPH + IH treatments. The cerebrospinal fluid (CSF) was collected and the DA levels were detected by high performance liquid chromatography (HPLC). The plasma prolactin (PRL) concentration was measured by radioimmunoassay (RIA). We found that IH reduced basal DA concentration in media prefrontal cortex (mPFC), but increased that in striatum, where DA level was also increased in rats treated with AMPH or AMPH + IH. Angiotensin II (Ang II) increased the DA release in mPFC and striatum and this effect was enhanced in AMPH + IH group. The stimulatory effect of IH on plasma PRL was attenuated in presence of AMPH. Tyrosine hydroxylase (TH) expression was decreased by IH, but increased by AMPH + IH in mPFC. IH or AMPH treatment decreased the expression of vesicular monoamine transporter-2 (VMAT-2) in rat brain. These data suggested that IH altered the DA release and changed the protein expression levels in different parts of rat brain treated with AMPH. IH may play a role in regulating DA metabolism in AMPH addiction.

Antisteroidogenic effects of hydrogen peroxide on rat granulosa cells.

Rat granulosa cells (GCs) were treated with human chorionic gonadotropin (hCG), 8-bromo-adenosine 3',5'-cyclic monophosphate (8-Br-cAMP), forskolin, phorbol 12-myristate 13-acetate (PMA), A23187 or pregnenolone in the absence or presence of hydrogen peroxide (H(2)O(2)). Different doses of trilostane were applied to GCs treated with steroidogenic precursors, that is, 25-hydroxy-cholesterol (25-OH-C) in the absence or presence of H(2)O(2). Results showed that all of the chemicals stimulated the progesterone (PG) release from rat GCs, but the stimulatory effects were inhibited by H(2)O(2) dose-dependently. 25-OH-C stimulated the PG release, which was inhibited by H(2)O(2) in the presence of trilostane. H(2)O(2) attenuated steroidogenic acute regulatory (StAR) protein expression, but did not alter the expression of cytochrome P450 side chain cleavage (P450scc) in Western blotting. This study indicated that H(2)O(2) inhibited PG production by GCs via cAMP pathway, protein kinase C (PKC) and the activities of intracellular calcium, P450scc and StAR protein.

Effects of nonylphenol on the production of progesterone on the rats granulosa cells.

We investigated the effects of nonylphenol (NP) on release of progesterone (PG) by granulosa cells (GCs) of rats in vitro and in vivo. First, GCs were treated with different doses of NP for 2-24 h alone or with human chorionic gonadotropin (hCG). Maximal PG secretion at 8 h noted, GCs were treated for 2 h with hCG, 8-bromo-adenosine 3':5'-cyclic monophosphate (8-Br-cAMP), forskolin, A23187, nifedipine, and pregnelonone to evaluate the NP effects on PG steroidogenesis. Results indicated that all of chemicals except nifedipine stimulated the PG release compared to vehicle, but the stimulatory effects could not be enhanced by different doses of NP. Second, GCs were isolated to react with hCG, 8-Br-cAMP and PD98059 after the immature female rats gavaged with different doses of NP (ONP) for 7 days. PG released significantly when rats treated with oral NP 100 compared to 0 µg/kg/day. Third, GCs collected from the female offspring of mother rats which gavaged with NP 100 µg/kg/day for 21 days during pregnancy (MONP) reacted with different doses of chemicals. The results showed that PG release in the presence of chemicals was significantly higher in ONP and MONP groups; however, this stimulation was not noted by dose-dependent. The plasma concentration of PG was higher in ONP (100 µg/kg/day) and the offspring of MONP groups. The steroidogenic acute regulatory (StAR) protein expressed higher in all three groups by Western blotting. This study results indicated that low dose of NP stimulated PG release in rat GCs by activation of StAR protein.

Effects of catechin, epicatechin and epigallocatechin gallate on testosterone production in rat leydig cells.

Catechins have been reported to have many pharmacological properties such as the effects of anti-oxidative, anti-inflammatory, anti-carcinogenic, anti-ultraviolet, and reduction of blood pressure as well as glucose and cholesterol levels. However, the effect of catechins on the reproductive mechanism is still unknown. In the present study, the effects of catechins on testosterone secretion in rat testicular Leydig cells (LCs) were explored. Both in vivo and in vitro investigations were performed. Purified LCs were incubated with or without catechin (CCN), epicatechin (EC), epigallocatechin gallate (EGCG, 10(-10)-10(-8) M) under challenge with human chorionic gonadotropin (hCG, 0.01 IU/ml), forskolin, SQ22536 (an adenylyl cyclase inhibitor), 8-bromo-adenosine 3':5'-cyclic monophosphate (8-Br-cAMP), A23187 (a calcium ionophore), and nifedipine (10(-5) M), respectively. To study the effects of catechins on steroidogenesis, steroidogenic precursors-stimulated testosterone release was examined. The functions of the steroidogenic enzymes including protein expression of cytochrome P450 side chain cleavage enzyme (P450scc) and steroidogenic acute regulatory (StAR) protein were investigated and expressed by Western blotting. Catechins increased plasma testosterone in vivo in male rats. In vitro, low-dose concentration of catechins increased gonadotropin releasing hormone (GnRH)-stimulated luteinizing hormone (LH) release by anterior pituitary gland and hCG-stimulated testosterone release by LCs of male rats. These results suggested that catechins stimulated testosterone production by acting on rat LCs via the mechanism of increasing the action of cAMP, but not P450scc, StAR protein or the activity of intracellular calcium. EC, one of the catechins increased the testosterone secretion by rat LCs via the enzyme activities of 17beta-hydroxysteroid dehydrogenase (17beta-HSD).

Attenuation of estradiol on the reduction of striatal dopamine by amphetamine in ovariectomized rats.

Amphetamine (AMPH) is a highly addictive drug of abuse which exhibits toxicity to dopaminergic neurons in long-term abusers. Estrogen seems to show neuroprotection in dopamine (DA) deficit caused by AMPH. The present study was to investigate the effects of estradiol on the levels of striatal DA in ovariectomized (Ovx) rats treated with or without AMPH. Female rats were Ovx for 2 weeks before administration of AMPH (5 mg/kg/day, i.p.) with or without 17beta-estradiol benzoate (EB) (25 microg/kg/day, s.c.) for 7 days. The striatal tissues were collected, homogenized with DA mobile phase, and centrifuged. The concentrations of DA in the supernatants were detected by HPLC. The protein expressions of dopamine transporter (DAT), vesicular monoamine transporter 2 (VMAT-2), and tyrosine hydroxylase (TH) were analyzed by Western blotting. The results indicated that AMPH could attenuate DA level significantly in striatum (P < 0.01). Comparing to control groups, administration of either EB or EB plus AMPH increased DA level (P < 0.01). The protein expression of striatal DAT was significant greater (P < 0.01) in rats treated with AMPH plus EB than AMPH treated animals. These results suggest that the DA levels in striatum can be enhanced by EB via an increase of DAT expression following administration of AMPH.

Effects of evodiamine and rutaecarpine on the secretion of corticosterone by zona fasciculata-reticularis cells in male rats.

Evodiamine (EVO) and rutaecarpine (RUT) are two bioactive alkaloid isolated from Chinese herb named Wu-Chu-Yu. Previous studies have shown that EVO and RUT possess thermoregulation, vascular regulation, anti-allergic, anti-nociceptive and anti-inflammatory activities. The mechanisms of EVO and RUT effect on steroidogenesis are not clear. The goal of this study was to characterize the mechanism by which EVO and RUT affect corticosterone production in rat zona fasciculata-reticularis (ZFR) cells. ZFR cells were isolated from adrenal glands of male rats and incubated with adrenalcorticotropin (ACTH, 10(-9) M), forskolin (an adenylyl cyclase activator, 10(-5) M), 8-bromo-adenosine 3':5'-cyclic monophosphate (8-Br-cAMP, a permeable cAMP analog, 10(-4) M), or steroidogenic precursors including 25-hydroxycholesterol, pregnenolone, progesterone, and deoxycorticosterone, 10(-5) M each, in the presence or absence of EVO and RUT respectively (0-10(-3) M) at 37 degrees C for 1 h. The concentrations of corticosterone, pregnenolone and progesterone in the media were measured by radioimmunoassay. After administration of ZFR cells with EVO or RUT (10(-4) M) for 60 and 120 min, Western blot analysis was employed to explore the influence of EVO and RUT on the expression of cytochrome P450 side chain cleavage enzyme (P450scc) and steroidogenic acute regulatory protein (StAR). EVO and RUT reduced both basal and ACTH-, forskolin-, as well as 8-Br-cAMP-stimulated corticosterone production in rat ZFR cells. The enhanced corticosterone production caused by the administration of four steroidogenic precursors was decreased following EVO or RUT challenge. These results suggest that EVO and RUT inhibit corticosterone production in rat ZFR cells via a mechanism involving: (1) a decreased activity of cAMP-related pathways; (2) a decreased activity of the steroidogenic enzymes, that is, 3beta-hydroxysteroid dehydrogenase (3beta-HSD) and 11beta-hydroxylase (P450c11), during steroidogenesis; and (3) an inhibition of StAR protein expression.