The involvement of the mTOR system/enzyme sirtuin 1 (SIRT1) intracellular signaling system in the control of ovarian functions and its role in mediating hormonal action on the ovary has been proposed, but this hypothesis should be supported by a demonstrated influence of hormones on mTOR/SIRT1. Therefore, the aim of our in vitro experiments was to examine the effect of the known hormonal regulators of ovarian functions, such as follicle-stimulating hormone (FSH), oxytocin (OT) and insulin-like growth factor I (IGF-I), on mTOR/SIRT1. The accumulation of SIRT1 in porcine ovarian granulosa cells cultured with and without these hormones (at doses of 1, 10 or 100 ng.ml-1 ) was evaluated using immunocytochemistry. It was observed that the addition of FSH (at 10 ng.ml-1 but not at 1 or 100 ng/ml) and OT (at all tested doses) increased the expression of SIRT1 in ovarian cells. In addition, 100 ng.ml-1 , but not at 1 or 10 ng.ml-1 , of IGF-I decreased SIRT1 accumulation. Our observations are the first demonstration that hormones can directly regulate the ovarian mTOR/SIRT1 system and that this system could mediate the action of hormonal regulators on the ovary.
t would be desirable to expand the existing general knowledge concerning direct action of metals on the ovary. Nevertheless, the results of testing of iron compound on porcine ovarian cells should be interpreted carefully because iron is an essential element which could also induce changes in cellular processes. The aim of this in vitro study was 1) to examine dose-dependent effects of iron on the secretory activity of porcine ovarian granulosa cells, and 2) to outline the potential intracellular mediators mediating these effects. Specifically, we evaluated the effect of iron sulphate on the release of insulin-like growth factor I (IGF-I) and progesterone, as well as the expression of markers of proliferation (cyclin B1) and apoptosis (caspase-3) in porcine ovarian granulosa cells. Concentrations of IGF-I and progesterone were determined by RIA, cyclin B1 and caspase-3 expression by immunocytochemistry (ICC). Our results show a significantly decreased IGF-I secretion by ovarian granulosa cells after iron sulphate addition at the doses 0.5 and 1.0 mg/ml. The iron sulphate additions at do ses 0.17 and 1.0 mg/ml had no effect on progesterone secretion. In contrast, iron sulphate addition at doses 0.17-1.0 mg/ml resulted in stimulation of cyclin B1 and caspase-3 expression. In conclusion, the present results indicate a direct effect of iron on 1) secretion of growth factor IGF-I but not steroid hormone progesterone, 2) expression of markers of proliferation (cyclin B1), or 3) apoptosis (caspase-3) of porcine ovarian granulosa cells. These results support an idea that iron could play a regulatory role in porcine ovarian function: hormone release, prolif eration and apoptosis., A. Kolesarova ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
The aim of this in vitro study was to examine the secretion activity (progesterone, 17β-estradiol and insulin-like growth factor-I) of rat ovarian fragments after molybdenum (Mo) addition. Rat ovarian fragments were incubated with ammonium molybdate (NH4)6Mo7O24.4H2O at the doses 90, 170, 330 and 500 μg.ml-1 for 24 h and compared with control group without Mo addition. Release of progesterone (P4), estradiol (17β-estradiol) and insulin-like growth factor I (IGF-I) by ovarian fragments was assessed by radioimmunoassay (RIA). Data show that P4 release by ovarian fragments was not affected by (NH4)6.Mo7O24.4H2O addition at all the doses used (90-500 μg.ml-1). However, addition of ammonium molybdate was found to cause a significant (P<0.05) dose-dependent decrease (at the doses 90, 170 and 500 μg.ml-1) in release of 17β-estradiol by ovarian fragments in comparison to control. Also, addition of ammonium molybdate significantly (P<0.05) inhibited IGF-I release at all the doses (90-500 μg.ml-1) used in the study. Results suggest ammonium molybdate induced inhibition in the release of growth factor IGF-I and its dosedependent effect on secretion of steroid hormone 17β-estradiol but not progesterone. These data contribute to new insights regarding the mechanism of action of Mo on rat ovarian functions., S. Roychoudhury, L. Detvanova, A. V. Sirotkin, R. Toman, A. Kolesarova., and Obsahuje bibliografii
Milk production, plasma bovine somatotropin (bST) and insulin-like growth factor I (IGF-1) were measured in dairy cows following a single subcutaneous injection of a slowly released preparation of either recombinant enterokinase linker bST (somidobove: 640 mg) or recombinant methionyl bST (sometribove: 500 mg). There was a 3-7-fold increase in plasma bST concentrations during the first three postinjection hours in cows treated with both sometribove (from 3.4±0.8 to 11.2±3.0 ng ml-1) or somidobove (from 2.3±0.3 to 17.5±2.6 ng ml-1). In the next 8 days the bST concentration in the bST-treated cows varied, but was still significantly increased above the controls. In the following days, the concentrations of bST did not differ from the controls. Plasma concentrations of IGF-1 increased nearly 2-fold as early as 24 h following recombinant bST administration and then continued to rise so that by 48 h postinjection they were nearly four times higher (control 16.2, bST-treated 61.7 ng ml-1). From 48 h after sometribove injection, IGF-1 concentrations remained at a plateau (varying between 60.4 and 85.7 ng ml-1) till day 11. Then it decreased slowly, but still remained higher on day 14 than those in placebo-treated cows (44.4±17.8 ng ml-1 in bST-treated animals; 12.2±7.5 ng ml-1 in the controls). Although IGF-1 level was increasing in all bST-treated animals, the absolute IGF-1 increase was not related to the increase in milk production.
T-2 toxin and its metabolite HT-2 toxin are one of the most toxic mycotoxins of type A-trichothecenes, which are produced mainly by Fusarium species. Therefore, study of Fusarium toxins T-2 toxin and HT-2 toxin is an essential issue because they could also play role in failures of reproductive functions as well as endocrine system of domestic animals. Assessment of the effect of A-trichothecene mycotoxin HT-2 toxin alone or combined with insulin-like growth factor (IGF-I), leptin and ghrelin on estradiol secretion by rabbit ovarian fragments in vitro was done. Rabbit ovarian fragments were incubated without (control group) or with HT-2 toxin, or its combinations with IGF-I, leptin and ghrelin at various concentrations for 24 h. Secretion of 17β-estradiol was determined by ELISA. Firstly, HT-2 toxin at the doses 10 and 100 ng.ml-1, but not at 1 ng.ml-1 decreased 17β-estradiol secretion by ovarian fragments. Secondly, 17β-estradiol secretion was not affected by HT-2 toxin exposure combined with growth factor IGF-I, metabolic hormones leptin and ghrelin. In conclusion, HT-2 toxin has potent direct dose-dependent effects on ovarian steroidogenesis in rabbits. These direct effects of HT-2 mycotoxin on ovarian steroidogenesis could impact negatively on the reproductive performance of rabbits., A. Kolesarova, N. Maruniakova, A. Kadasi, M. Halenar, M. Marak, A. V. Sirotkin., and Obsahuje bibliografii
The system of IGF-I and its binding proteins may be involved in the pathogenesis of vascular damage in Type 1 diabetes. The aim of this study was to analyze the relationship between this system and the microvascular reactivity in Type 1 diabetes as measured by laser-Doppler flowmetry. Twenty-two Type 1 diabetic patients (13 women and 9 men) with microangiopathy and fifteen healthy subjects (8 women and 7 men) were examined clinically, underwent laser-Doppler flowmetry and intima-media thickness measurements. Fasting serum levels of IGF-I, free IGF-I, IGFBPs and lipids were examined. The microvascular reactivity was impaired in Type 1 diabetic patients. Maximal perfusion during post-occlusive reactive hyperemia (PORHmax) and during thermal hyperemia (THmax) was significantly decreased in Type 1 diabetes (p<0.01). Percentage perfusion increase in both tests (PORH and TH) was lower in Type 1 diabetes mellitus (p<0.01) and the reaction after heating was slower in diabetic patients (THmax/t) (p<0.01). We did not find any significant dependence of microvascular reactivity on the parameters of IGF-I or its binding proteins. We conclude that the microvascular reactivity is impaired in Type 1 diabetes mellitus, but this impairment is not clearly dependent on the activity of the IGF-I system. It is probably only a complementary pathogenic factor., M. Kršek, M. Prázný, J. Škrha, V. Justová, Z. Lacinová, T. Haas., and Obsahuje bibliografii