Insulin-like growth factor-I as a follicular growth promoter during early pregnancy in thoroughbred mares.
To elucidate the physiological role of insulin-like growth factor-I (IGF-I) during early pregnancy in mares, number of ovarian follicles was monitored ultrasonically during different stages of the first trimester of pregnancy in 36 thoroughbred mares. From 9 of 36 mares, blood samples were collected weekly from the mating day till the end of the first trimester of pregnancy and plasma IGF-I profiles were examined with other hormones, like follicle stimulating hormone (FSH), luteinizing hormone (LH), ir-inhibin, progesterone and estradiol-17beta. Plasma IGF-I level fluctuated throughout the studied period with four peaks on the 7th, 28th, 49th and 84th days of pregnancy. Plasma IGF-I showed a positive correlation with plasma FSH (P<0.05), whereas no correlation was found with other hormones during the studied period. Plasma IGF-I had no correlation with the foetal size, but positive correlation with the number of large (> 30 mm) and medium (10-30 mm) follicles. These results suggested that IGF-I might produce from the medium and large follicles during early pregnancy and promote to develop their growth via pituitary FSH mediated effects in the mares.
Derar
Refaat
R
Department of Theriogenology, Faculty of Veterinary Medicine, Assiut University, Assiut, Egyt.
Haramaki
Shigeyuki
S
Hoque
Shafiqul
S
Hashizume
Tsutomu
T
Osawa
Takeshi
T
Taya
Kazuyoshi
K
Watanabe
Gen
G
Miyake
Yoh-Ichi
Y
D000818:Animals; D005260:Female; D006736:Horses / Q000097:blood / Q000502:physiology*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism / Q000502:physiology*; D006080:Ovarian Follicle / Q000254:growth & development*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*; D013997:Time Factors
D007334:Insulin-Like Growth Factor I