Reproduction in Domestic Animals - Facultad de Ciencias Veterinarias

16 t h International Congress on Animal Reproduction
Poster Abstracts 107
P238
Immunocytochemical localization of leptin (Ob) and leptin
receptor (Ob-R) in preovulatory and in vitro matured
horse oocytes related to prepuberty and different weight
breeds
Lange Consiglio, A 1 *, Arrighi, S 2 , Bosi, GP 2 , Aralla, M 2 , Cremonesi, F 2
1Veterinary Clinical Sciences, Reproduction Unit, University of Milano, Faculty
of Veterinary Medicine, Italy; 2 Department of Veterinary Science and
Technologies, University of Milano, Faculty of Veterinary Med, Italy
The onset of puberty in humans and animals is associated with an
increase in fat and consequent increase in circulating leptin,
suggesting that leptin may be required for normal growth and
development of reproductive organs. Moreover, leptin amount in the
blood is proportional to body energy stores and/or body mass, so,
inadequate nutrition might impair reproductive function leading, for
example, to the delayed onset of puberty. A similar relationship
between nutrition and reproductive efficiency is not understood in the
mare where, besides many reports quantifying the correlation of
circulating concentration of leptin with body condition scores, only
few informations exist about the presence of leptin (Ob) and leptin
receptor (Ob-R) in the ovary or in the oocyte. Taking this into
account, we carried out an immunocytochemical study to investigate
the presence of Ob and Ob-R in compact cumulus oocytes recovered
from fillies and from mares of light or heavy body weight breeds after
slaughtering during the autumnal transition. The occurrence of
immunofluorescence was determined by scanning laser confocal
microscopy in oocytes immediately upon collection and after in vitro
maturation (IVM) using monoclonal antibody conjugated to a
fluorescent label. IVM was accomplished in TCM199 supplemented
with 1 mM pyruvate, 0.1 IU LH, 0.1 IU FSH, 100 ng IGF, 50 ng EGF,
1 µl ITS and 1 µl estrogen per ml. Oocytes were incubated for 40 h at
38°C at 5% CO2. Both Ob and Ob-R, detected in immature oocytes of
all kinds of animals analyzed, were uniformly distributed throughout
the ooplasm, but the intensity of reaction was lower either in light
weight mares or in fillies oocytes, than in oocytes of heavy weight
mares. After IVM, heavy breed mares had a higher proportion of
oocytes that reached metaphase II than light mares and fillies
(35.53±2.71%, 19,84±1.48% and 15,82±1,52 respectively; P