Effects of leptin and neuropeptide Y (NPY) on hormones release in female rats.
OBJECTIVE
The aim of this study was to investigate the influence of NMMA on the mechanism of leptin and NPY action in in vivo and in vitro on pituitary hormone release by female rats in diestrus.


METHODS
In vivo experiments based on four-day ip injections of: 1) murine recombinant leptin (mrLep); 2) human NPY; 3) saline; 4) NMMA (50 microg) was applied prior to administration of mrLep; 5) NMMA (50 microg) was applied prior to administration of NPY; 6) NMMA (50 microg); 7) NMMA (350 microg) was applied prior to administration of mrLep; 8) NMMA (350 microg). The blood samples for LH and FSH were collected after decapitation of animals on the fifth day of study. In vitro experiments studied the effects of these peptides on LH release from pituitary cell culture.


RESULTS
In vivo: Leptin+ NMMA (50 microg) stimulated LH. NPY+ NMMA (50 microg) increased LH. NMMA (350 microg) stimulated FSH release. In vitro: The stimulatory effect of leptin on LH release in vitro was observed after 120 min of incubation, but after 60 mins of incubation the inhibitory effect of leptin on LH release was increased by NMMA. Leptin +NMMA (vs NMMA) decreased LH release with highest statistical significance. NPY 10 nM 60 min after incubation decreased LH release. There was no effect of NMMA on LH release.


CONCLUSIONS
In vivo results show, that NO probably mediates in leptin action on LH release. Moreover, effects of leptin on LH release from cultured pituitary cells are dependent on time of incubation. NPY decreased LH release in vitro.
Borowiec
Monika
M
Neoruoendocrinology Department, Medical Centre of Postgraduate Education, Fieldorfa 40, 04-158 Warsaw, Poland. zncmkp@free.polbox.pl
Wasilewska-Dziubiñska
Elzbieta
E
Chmielowska
Magdalena
M
Woliñska-Witort
Ewa
E
Baranowska
Boguslawa
B
D000818:Animals; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood*; D020738:Leptin / Q000494:pharmacology*; D007986:Luteinizing Hormone / Q000097:blood*; D009478:Neuropeptide Y / Q000494:pharmacology*; D009569:Nitric Oxide / Q000378:metabolism; D010902:Pituitary Gland / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D011921:Rats, Inbred WKY; D019323:omega-N-Methylarginine / Q000494:pharmacology
D004791:Enzyme Inhibitors; D020738:Leptin; D009478:Neuropeptide Y; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone