Effects of homologous pituitary hormone treatment on serum insulin-like growth-factor-binding proteins (IGFBPs) in hypophysectomized tilapia, Oreochromis mossambicus, with special reference to a novel 20-kDa IGFBP.
In the circulation, insulin-like growth factors (IGFs) bind to high-affinity-binding proteins. Insulin-like growth-factor-binding proteins (IGFBPs) appear to be present in all vertebrates. To examine the hormonal regulation of serum IGFBPs in a fish, tilapia (Oreochromis mossambicus) were hypophysectomized (Hx) and then treated with homologous tilapia growth hormone (tGH) or either form of tilapia prolactin (tPRL177, tPRL188). Hormones were administered at three doses: 15, 150, and 500 ng/g of body weight. Serum IGFBP profiles were analyzed by SDS-PAGE and Western ligand blotting using 125I-rhIGF-I as a probe. A prominent IGFBP (ca 20 kDa), termed IGFBP-20K, appeared after hypophysectomy. Administration of tGH at all dose levels suppressed this BP and restored levels back to those seen in sham-operated control fish. tPRL177 and tPRL188 were also effective in lowering IGFBP-20K levels. Levels of the 29-kDa IGFBP (termed IGFBP-29K) increased after hypophysectomy; tGH at all doses and tPRL177 at the two lower doses further increased these levels. All doses of tGH, tPRL177, and tPRL188 significantly increased levels of the 32-kDa IGFBP (termed IGFBP-32K). Hypophysectomy significantly lowered levels of the 40-kDa IGFBP (termed IGFBP-40K) below levels seen in the sham-operated controls. tGH treatment significantly raised IGFBP-40K levels at all doses examined, but not to the levels seen in intact tilapia. The 42-kDa IGFBP (termed IGFBP-42K) was not affected by hypophysectomy or hormone replacement. Our data suggest that the novel 20-kDa IGFBP and the 40-kDa IGFBP species may be similar in function to mammalian IGFBP-1 and IGFBP-3, respectively.
Park
R
R
Department of Integrative Biology and Cancer Research Laboratory, University of California, Berkeley, California 94720-3140, USA.
Shepherd
B S
BS
Nishioka
R S
RS
Grau
E G
EG
Bern
H A
HA
D000818:Animals; D015153:Blotting, Western; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D013006:Growth Hormone / Q000494:pharmacology; D007016:Hypophysectomy; D018969:Insulin-Like Growth Factor Binding Proteins / Q000097:blood*; D008297:Male; D008970:Molecular Weight; D010907:Pituitary Hormones / Q000494:pharmacology*; D011388:Prolactin / Q000494:pharmacology; D017210:Tilapia / Q000097:blood*
D018969:Insulin-Like Growth Factor Binding Proteins; D010907:Pituitary Hormones; D011388:Prolactin; D013006:Growth Hormone