The effect of low concentrations of hydrogen peroxide (10-100 µM) on sperm motility and on the activity of the sperm enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDS) was investigated. Incubation of semen samples with 10 and 100 µM hydrogen peroxide increased the content of spermatozoa with progressive motility by 20 and 18%, respectively, and enhanced the activity of GAPDS in the sperm cells by 27 and 20% compared to a semen sample incubated without additions. It was also found that incubation with 10 µM hydrogen peroxide increased the content of reduced glutathione (GSH) in sperm cells by 50% on average compared to that in the control samples. It is supposed that low concentrations of hydrogen peroxide activate the pentose phosphate pathway, resulting in NADPH synthesis and the reduction of the oxidized glutathione by glutathione reductase yielding GSH. The formed GSH reduces the oxidized cysteine residues of the GAPDS active site, increasing the activity of the enzyme, which in turn enhances the content of sperm cells with progressive motility. Thus, the increase in motile spermatozoa in the presence of low concentrations of hydrogen peroxide can serve as an indicator of normal functioning of the antioxidant defense system in sperm cells.
Immunoperoxidase method combined with cytofluorimetry showed that in contrast to hepatocytes, enhanced expression of prolactin receptors on rat cholangiocytes induced by common bile duct ligation cannot be suppressed by the prolactin secretion inhibitor bromocriptine.
Key Words: prolactin receptors; rat liver cells; common bile duct ligation; bromocriptine; immunohistochemistryExpression of prolactin receptors (PRL-R) in hepatocytes is regulated by a multihormonal assembly, that includes prolactin (PRL), the major positive regulator of PRL-R, sex steroids, insulin, thyroid hormones, and glucocorticoids [2]. Hepatotropic effects of PRL, in particular, induction of ornithine decarboxylase [7], phosphoenolpyruvate carboxykinase [12], and protein kinase C [5], expression of the growth hormone genes [7], stimulation of DNA synthesis [6], and DNA hypomethylation [9] are studied in detail.Unlike hepatocytes, cholangiocytes express little or no PRL-R in mature rats, but intensely express these receptors during active proliferation (in prepubertal animals [1]) or after common bile duct ligation (CBDL) [3]. The physiological role of increased sensitivity of cholangiocytes to PRL during the prepubertal period remains unclear. Another peculiarity is that the expression of PRL-R in cholangiocytes does not depend on sex steroids [3]. These data suggest different mechanisms of regulation of PRL-R expression in hepatocytes and cholangiocytes. To verify this assumption we studied the effect of PRL on PRL-R expression in rat cholan-
MATERIALS AND METHODSExperiments were carried out o11 random-bred albino rats of both sexes weighing 200-220 g. The common bile duct was ligated by a standard method described previously [4].On days 5-13 postoperation, 5 males and 8 females were subcutaneously injected with 10 nag/ kg bromocriptine dissolved in 50% ethanol (2 nag/ 0.5 ml/rat). Control animals (4 males and 8 females) received 0.5 lnl 50% ethanol every days. The animals were decapitated on day 14 postoperation. The liver was fixed in 4% paraform for 18-20 h at 4~ and embedded in paraplast; PRL-R were visualized by indirect immunoperoxidase method [11]. To this end, 3-gm-thick sections pretreated with 10 mM sodium periodate and 0.01% sodium borohydrite were incubated with mouse monoclonal antibodies clone U6 (0.1 mg/ml IgG fraction from ascitic fluid, kindly provided by Dr. P. A. Kelly, France) in 0.05
267 scent HDL. The content of total serum Ch dropped by 38% (p<0.01) and by 41% (p<0.01) after the administration of compound II and compound I, respectively. However, the level of c~-Cli did not drop, and in the case of compound II it even rose 22%, i.e., the drop of total Ch occurred due to LDL and VLDL Ch. Both test compounds increased the content of Ch in the liver, whereas accumulation of TG was observed only in the case of compound I (Table 2).Thus, the effect of compounds I and II on serum LP and on the content of Ch in blood serum and in the liver surpasses that of estradiol, which does not normalize the LP spectrum in ovariectomized animals and even alters it adversely in experimental animals. Compound II possesses a less pronounced hypolipidemic activity in comparison with compound I; however, its effect on the serum LP spectrum is more favorable.
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