Follicular and luteal expression of insulin-like growth factors I and II and the type 1 IGF receptor in the bovine ovary.
The localization of mRNAs for insulin-like growth factors I (IGF-I) and II (IGF-II) and the type 1 IGF receptor (IGF-1R) in bovine follicles and corpora lutea was determined using in situ hybridization on sectioned ovaries collected from nonpregnant, cyclic Holstein cows in either the follicular (n = 3) or luteal (n = 5) phases of the cycle. Concentrations were measured as absorbance units of individual regions or follicles from autoradiographs. There was intense follicular expression of mRNAs encoding IGF-II and IGF-1R. For mRNA encoding IGF-II, expression was significantly higher in smaller follicles (< 5 mm diameter, P < 0.01) and, in this size range, expression was significantly greater in healthy compared with atretic follicles (P < 0.01). For mRNA encoding IGF-1R, there was no effect of size but concentrations were again significantly greater in healthy compared with atretic follicles of < 5 mm. In medium (5-10 mm) and large (> 10 mm) follicles, there was no effect of health for expression of either IGF-II or IGF-1R. mRNA encoding IGF-II was found exclusively in the theca, whereas mRNA encoding IGF-1R was confined to the granulosa layer. IGF-I expression was not detectable in 83% of the 53 follicles examined. In the remaining 17% of follicles, expression was very low and was unrelated to size or state of atresia. mRNAs encoding IGF-I, -II and IGF-1R were all present in the corpus luteum, whereas only those for IGF-II and IGF-1R were found in ovarian stroma. These data indicate that the insulin-like growth factors play a significant role in follicular and luteal development in the bovine ovary. Locally produced IGF-II is probably an important regulator of follicular growth, whereas most of the IGF-I present in follicular fluid is likely to be derived from the circulation.
Perks
C M
CM
Reproduction and Development Group, Royal Veterinary College, Hertfordshire, UK.
Peters
A R
AR
Wathes
D C
DC
D000818:Animals; D002417:Cattle / Q000378:metabolism*; D003338:Corpus Luteum / Q000737:chemistry; D005260:Female; D005498:Follicular Phase; D015870:Gene Expression; D006107:Granulosa Cells / Q000737:chemistry; D017403:In Situ Hybridization; D007334:Insulin-Like Growth Factor I / Q000235:genetics; D007335:Insulin-Like Growth Factor II / Q000235:genetics; D008183:Luteal Phase; D006080:Ovarian Follicle / Q000737:chemistry; D010053:Ovary / Q000737:chemistry*; D012333:RNA, Messenger / Q000032:analysis*; D017526:Receptor, IGF Type 1 / Q000235:genetics*; D013002:Somatomedins / Q000235:genetics*; D013799:Theca Cells / Q000737:chemistry
D012333:RNA, Messenger; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D017526:Receptor, IGF Type 1