Characterization of insulin and insulin-like growth factor-I ovarian receptors during the reproductive cycle of carp (Cyprinus carpio).
Insulin and insulin-like growth factor-I (IGF-I) receptors were characterized in glycoprotein fractions prepared by wheat germ agglutinin-agarose affinity chromatography from the ovaries of carp. Insulin-specific overall binding in carp ovaries was 6- to 11-fold lower than IGF-I binding (2.7 +/- 0.48% vs. 22.8 +/- 3.6% per 20 microg glycoprotein). Cold IGF-I displaced radiolabeled IGF-I binding in doses 1000- to 3000-fold lower than cold insulin. On the other hand, cold insulin displaced radiolabeled insulin binding at concentrations 5- to 30-fold lower than cold IGF-I. The alpha-subunit molecular masses of carp insulin and IGF-I receptors were smaller than the alpha-subunit molecular mass of rat insulin receptor (125 and 120 vs. 135 kDa, respectively). Autophosphorylation of carp beta-subunit insulin and IGF-I receptors showed similar molecular masses that did not differ from the molecular mass of rat insulin beta subunit. Receptor tyrosine kinase activity was stimulated in a dose-dependent manner by insulin and IGF-I. Insulin and IGF-I stimulated tyrosine kinase activity and reached a maximum, respectively, of 224 +/- 14% and 279 +/- 7% of basal phosphorylation. Insulin and IGF-I binding characteristics were measured through different stages of follicular development. High specific binding of both peptides in primary oocyte growth (5.6 +/- 0.8% and 50 +/- 10% per 20 microg glycoprotein for insulin and IGF-I, respectively) decreased to a minimum at the end of vitellogenesis, followed by a slight increase later, in the preovulatory stage. The presence of insulin and IGF-I receptors in carp ovaries and the changes in percentage of binding throughout the reproductive cycle suggest that, in carp, the roles of insulin and IGF-I depend on the ovarian maturation stage.
Maestro
M A
MA
Departament de Fisiologia, Facultat de Biologia, Universitat de Barcelona, Spain.
Méndez
E
E
Párrizas
M
M
Gutiérrez
J
J
D000818:Animals; D002347:Carps / Q000254:growth & development / Q000378:metabolism*; D005260:Female; D008970:Molecular Weight; D010053:Ovary / Q000254:growth & development / Q000378:metabolism*; D011487:Protein Conformation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D051381:Rats; D017526:Receptor, IGF Type 1 / Q000737:chemistry / Q000378:metabolism*; D011972:Receptor, Insulin / Q000737:chemistry / Q000378:metabolism*; D012098:Reproduction; D013045:Species Specificity
D011505:Protein-Tyrosine Kinases; D017526:Receptor, IGF Type 1; D011972:Receptor, Insulin