Gh and IGF-I increase leptin receptor expression in prepubertal pig ovaries: the role of leptin in steroid secretion and cell apoptosis.
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.
Gregoraszczuk
Ewa L
EL
Laboratory of Reproductive Physiology and Toxicology, Department of Animal Physiology, Institute of Zoology, Jagiellonian University, Ingardena 6, 30-060 Krakow, Poland. greg@zuk.iz.uj.edu.pl
Rak
Agnieszka
A
Wójtowicz
Anna
A
Ptak
Anna
A
Wojciechowicz
Tatiana
T
Nowak
K W
KW
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000378:metabolism; D030762:Estrous Cycle; D005260:Female; D013006:Growth Hormone / Q000378:metabolism / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism / Q000494:pharmacology*; D020738:Leptin / Q000494:pharmacology* / Q000502:physiology*; D006080:Ovarian Follicle / Q000378:metabolism; D010053:Ovary / Q000378:metabolism*; D011374:Progesterone / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D011956:Receptors, Cell Surface / Q000378:metabolism*; D054411:Receptors, Leptin; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D013552:Swine
D020738:Leptin; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D054411:Receptors, Leptin; D011374:Progesterone; D004958:Estradiol; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone