Insulin-like growth factor-I and -II in the ovary of a bony fish, Oreochromis mossambicus, the tilapia: in situ hybridisation, immunohistochemical localisation, Northern blot and cDNA sequences.
There is accumulating evidence that insulin-like growth factor (IGF)-I and IGF-II are present in the mammalian ovary but comparable studies on bony fish remain scarce. Thus, the present study aims to analyse several parameters of the IGFs in the ovary of a bony fish, the tilapia, (Oreochromis mossambicus). Molecular biological and morphological techniques were applied. The IGF-I and IGF-II cDNA sequences established from the ovary indicate that the same molecules are present in ovary and liver. Northern blot analysis revealed four IGF-I mRNA transcripts (6.0, 3.9, 1.9, 0.5 kb) and three IGF-II mRNA transcripts (5.0, 4.0, 2.0 kb) in ovary and liver. The amounts of IGF-I and IGF-II mRNA in the ovary were considerably high when compared to those in liver (IGF-I: 80.7%; IGF-II: 63.7%). The expression of IGF-I mRNA and IGF-II mRNA in the ovary were studied by in situ hybridisation and the peptides located by immunohistochemistry. The expression of IGF-I varied between the different developmental stages. Both IGF-I mRNA and IGF-I immunoreactivity were present in small oocytes. Moderate IGF-I expression and immunoreactivity occurred in granulosa cells of follicles at the lipid stage. A high IGF-I expression was observed in the granulosa and theca cells surrounding oocytes at the yolk globule stages and mature oocytes but neither IGF-I mRNA nor IGF-I immunoreactivity occurred in oocytes of the later stages. Thus, the IGF-I production seems to change from the young oocyte to the surrounding follicle cells at the later stages. In contrast, IGF-II mRNA and IGF-II-immunoreactivity occurred only in granulosa cells of the late follicle stages. The results suggest that both IGF-I and IGF-II are involved in the maturation of bony fish oocytes and in follicle development in a paracrine/autocrine manner. IGF-I and IGF-II may exert their effects at different stages of development. Furthermore, the intraovarian IGF-I and IGF-II systems seem to have a long phylogenetic history indicating the importance of the IGFs in reproductive biology.
Schmid
A C
AC
Division of Neuroendocrinology, Institute of Anatomy, University of Zürich, Switzerland.
Näf
E
E
Kloas
W
W
Reinecke
M
M
D000818:Animals; D015152:Blotting, Northern; D018076:DNA, Complementary; D005260:Female; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000235:genetics*; D007335:Insulin-Like Growth Factor II / Q000032:analysis / Q000235:genetics*; D008099:Liver / Q000166:cytology / Q000378:metabolism; D008969:Molecular Sequence Data; D010053:Ovary / Q000166:cytology / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D017210:Tilapia / Q000235:genetics*; D014158:Transcription, Genetic
D018076:DNA, Complementary; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II