Inhibitory effects of stress-activated nitric oxide on antioxidant enzymes and testicular steroidogenesis

Testicular oxidative stress. Effects of experimental varicocele in adolescent rats

OBJECTIVE

This present study was undertaken to determine the levels of malondialdehyde (MDA), nitric oxide (NO) and total antioxidant status (TAS) in testes of adolescent rats with experimental bilateral varicocele and to determine the effects of oxidative stress on testis produced by varicocele.

METHODS

6-week-old, male Wistar rats, weighing 146-334 g (228.37 +/- 41.34 g), were randomly allocated into two groups. The first group underwent selective and bilateral partial ligation of the spermatic vein (n = 28), and the second group underwent a sham operation and served as the controls (n = 15). Animals were sacrificed 12 weeks after surgery and dilatation of the spermatic veins was observed in the first study group. Bilateral orchiectomy was performed in all rats, and MDA, NO and TAS levels were measured.

RESULTS

In the study group, the mean MDA (SEM) level was 15.58 +/- 6.07 micromol/g protein, and in the control group, it was 11.59 +/- 3.86 micromol/g protein, respectively; this difference was statistically significant (p < 0.05). The mean NO level was 82.73 +/- 77.84 nmol/g protein in the study group, whereas 28.65 +/- 20.18 nmol/g protein in the control group, this difference was also statistically significant (p < 0.005). The mean TAS levels of the study and control groups were 0.91 +/- 0.32 and 1.78 +/- 0.46 nmol/g tissue, respectively, and this difference was also statistically significant (p < 0.001). But there was no correlation between these three parameters (MDA<-->TAS: r = -0.103, p > 0.05; MDA<-->NO: r = -0.104, p > 0.05; NO<-->TAS: r = -0.123, p > 0.05).

CONCLUSION

These findings suggest that varicocele may change the testicular oxidative status and may play a role in testicular dysfunction that causes infertility.

Treatment with tetrahydrobiopterin reduces blood pressure in male SHR by reducing testosterone synthesis

Treatment with tetrahydrobiopterin (BH(4)) reduces blood pressure in spontaneously hypertensive rats (SHR). In the present study, we tested the hypothesis that chronic BH(4) reduces blood pressure in male SHR by reducing testosterone biosynthesis mediated by increasing nitric oxide (NO). Male SHR, aged 17-18 wk, intact or castrated, were treated for 1 wk with BH(4) (20 mg.kg(-1).day(-1) ip). After 1 wk, mean arterial pressure (MAP), serum testosterone, and nitrate/nitrite excretion (NO(x)) were measured. MAP was significantly higher in intact males than castrated males (179 +/- 2 vs. 155 +/- 4 mmHg, P < 0.001). In intact males, BH(4) caused a 17% reduction in MAP (148 +/- 2 mmHg), had no effect on NO(x), and reduced serum testosterone by 85% (24.09 +/- 2.37 vs. 3.72 +/- 0.73 ng/dl; P < 0.001). In castrated males, BH(4) had no effect on MAP (152 +/- 5 mmHg) but increased NO(x) by 38%. When castrated males were supplemented with testosterone, MAP increased to the same level as in intact males (180 +/- 7 mmHg), and BH(4) had no effect on MAP (182 +/- 7 mmHg) or NO(x). NO has been shown to decrease testosterone biosynthesis. Chronic sodium nitrite (70 mg.kg(-1).day(-1) x 1 wk) decreased MAP in intact males (150 +/- 4 mmHg) but had no effect on serum testosterone (21.46 +/- 3.08 ng/dl). The data suggest that BH(4) reduces testosterone synthesis and thereby reduces MAP in male SHR, an androgen-dependent model of hypertension. The mechanism(s) by which BH(4) reduces serum testosterone levels are not clear, but the data do not support a role for NO as a mediator.

Aluminum-induced suppression of testosterone through nitric oxide production in male mice

Excessive nitric oxide (NO) production in mice serum and testis due to aluminum (Al) exposure has been shown in previous studies. The aim of this study was to further investigate the role of NO on aluminum-suppressed testosterone level in male CD-1 mice. Each animal in six groups, was given intraperitoneal injections of either saline, aluminum chloride (AlCl(3)), l-N(6)-(1-iminoethyl) lysine (NO synthase inhibitor, l-NIL), or Al chloride along with l-NIL for a period of 12 days. These groups were denoted as C (control, saline), AL (35mg Al/kg/day, saline), NIL240 (total 240mg l-NIL/kg, saline), ALNIL240 (35mg Al/kg/day, total 240mg l-NIL/kg), ALNIL60 (35mg Al/kg/day, total 60mg l-NIL/kg), and NIL60 (total 60mg l-NIL/kg, saline). Results indicated that serum/testicular aluminum levels increased significantly in aluminum-treated animals compared to the controls, whereas the values observed from groups ALNIL240 than AL/ALNIL60 were markedly lower. Aluminum administration significantly increased NO production and decreased both testicular adenosine 3',5'-cyclic monophosphate (cAMP) and testosterone levels. A lower level of NO and higher concentrations of cAMP and testosterone observed in the ALNIL240 group indicated that the protective effect of NO synthase blockage was significant, although incomplete. In addition, aluminum induction significantly elevated the testicular cholesterol, but the values were lower in the ALNIL240 group than the AL or the ALNIL60 group. Finally, it was suggested that aluminum compounds exerted a significant adverse effects on the steroidogenesis and cAMP, which aided in the transport of cholesterol to the inner mitochondrial membrane. Furthermore, nitric oxide synthase blockage prevented aluminum-induced reproductive toxicity.