Authors:Ewa L. Gregoraszczuk, Agnieszka Rak, Anna Wójtowicz, Anna Ptak, Tatiana Wojciechowicz and K. W. Nowak
Leptin (L) is recognised as an important regulator of puberty and a factor which controls reproduction. Whole pig ovarian follicles were incubated with different doses of leptin (2, 20 and 200 ng/ml) added alone or in combination with 100 ng/ml of GH or 50 ng/ml of IGF-I. The expression of the functional long form leptin receptor (Ob-Rb) mRNA was examined by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) in follicular cells cultured with GH or IGF-I. Both GH and IGF-I increased leptin receptor expression in prepubertal pig ovaries. In separate experiments, the action of leptin on ovarian follicular steroidogenesis and cell apoptosis was examined. After 24 h of incubation with leptin alone or in combination with GH or IGF-I, oestradiol (E2) levels were determined in the culture medium while follicular tissue was used for the estimation of caspase-3 activity. Leptin increased E2 secretion and significantly diminished caspase-3 activity at all doses used. Both GH and IGF-I stimulated oestradiol secretion and decreased caspase-3 activity. No differences were demonstrable in oestradiol secretion and caspase-3 activity between cells treated with GH plus leptin and GH alone or cells treated with IGF-I plus leptin as compared to cultures treated with GH or IGF-I alone. However, GH diminished leptin-stimulated oestradiol secretion while IGF-I was without effect on it. Both GH and IGF-I reversed the anti-apoptotic action of leptin. In conclusion, we infer that (1) leptin directly affects ovarian function in prepubertal animals by its action on oestradiol secretion and cell apoptosis, (2) GH and IGF-I modulate the action of leptin, and (3) at least in part, the direct effect of GH/IGF-I on leptin production is due to an action on leptin receptor expression.
Authors:Adauto Chiamenti, Cristiano Filho, Marcelo Moura, Fabíola Paula-Lopes, Jairo Neves, Cícero Neto, Paulo Gonçalves, Paulo Lima and Marcos Oliveira
. H. (2000): High insulin-like growth factor I (IGF-I) and insulin concentrations trigger apoptosis in the mouse blastocyst via down-regulation of the IGF-I receptor. Endocrinology 141 , 4784–4792.
Moley K. H
Authors:Soheil Biglari, Alireza Ghardashi Afousi, Farnoosh Mafi and Fatemeh Shabkhiz
regulation appear to be two signal transduction pathways: insulin-like growth factor-I/Akt/mammalian target of rapamycin (IGF-I/Akt/mTOR) and myostatin/Smad [ 1 ]. Increased protein synthesis induced by activation of the IGF-I/Akt/mTOR signal transduction
Authors:Judith Anna Nikolić, Olgica Nedić, H. Šamanc, S. Aleksić, B. Miščević and Margit Kulcsár
, W. H. , Parker , K. A. , Borowsky , S. , Trivedi , B. and Kapadia , M. ( 1982 ): Measurement of somatomedin-related peptides in fetal, neonatal and maternal rat serum by insulin-like growth factor (IGF)-I radioimmunoassay, IGF
Authors:Vera Faigl, Mónika Keresztes, Margit Kulcsár, Sándor Nagy, Zsuzsanna Keresztes, Georgios Amiridis, László Solti, Gyula Huszenicza and Sándor Cseh
The objective of this study was to evaluate the effect of long-term melatonin treatment applied during the non-breeding season on semen characteristics, endocrine function of testicles and baseline level of insulin-like growth factor-I (IGF-I) in Awassi rams kept in the temperate continental zone of Europe and used as semen donors in an artificial insemination (AI) programme. On 23 February (day 0), slow-release melatonin implants were inserted subcutaneously into rams (n = 8). Control animals (n = 8) received no treatment. In both groups, basic semen parameters (concentration, total motility, fast and slow forward motility, morphology), GnRH-induced testosterone response and basal IGF-I concentration were evaluated on days 0, 47 and 71. No differences were found in concentration of spermatozoa, total motility, and numbers of spermatozoa with fast and slow progressive motility and normal/abnormal morphology between the melatonin-treated and the control group. However, in melatonin-treated animals, basal and GnRH-induced testosterone levels were slightly elevated on day 47 and became significantly higher on day 71 (P < 0.05) as compared to controls. There was no difference in plasma IGF-I levels between the groups. In conclusion, slow-release melatonin applied during the non-breeding season improves testicular testosterone production but does not influence the semen characteristics and the IGF-I level of semen donor Awassi rams used in an AI programme and kept in the temperate continental zone of Europe.
Authors:Margit Kulcsár, Gabriella Dankó, Carole Delavaud, C. Mircu, Anna J. Nikolic, A. Gáspárdy, H. Cernescu, Y. Chilliard, S. Cseh, P. Rudas and Gy. Huszenicza
-like growth factor-I (IGF-I) on cell numbers and steroidogenesis of bovine thecal cells: role of IGF-I receptors. Biol. Reprod. 54 , 255-263.
Interactions among basic fibroblast growth factor, epidermal growth factor, insulin, and
Authors:Anna Ptak, Ewa L. Gregoraszczuk and J. Rząsa
Apa, R., Di Simone, N., Ronsisvalle, E., Miceli, F., de Feo, D., Caruso, A., Lazone, A. and Mancuso, S. 1996: Insulin-like growth factor (IGF)-I and IGF-II stimulate progesterone production by human luteal cells