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
R. Park et al., 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, GEN C ENDOC, 117(3), 2000, pp. 404-412
In the circulation, insulin-like growth factors (IGFs) bind to high-affinit
y-binding proteins. Insulin-like growth-factor-binding proteins (IGFBPs) ap
pear to be present in all vertebrates, To examine the hormonal regulation o
f serum IGFBPs in a fish, tilapia (Oreochromis mossambicus) were hypophysec
tomized (Hx) and then treated with homologous tilapia growth hormone (tGH)
or either form of tilapia prolactin (tPRL(177), tPRL(188)). Hormones were a
dministered at three doses: 15, 150, and 500 ng/g of body weight. Serum IGF
BP profiles were analyzed by SDS-PAGE and Western ligand blotting using I-1
25-rhIGF-I as a probe. A prominent IGFBP (ca 20 kDa), termed IGFBP-20K, app
eared after hypophysectomy. Administration of tGH at all dose levels suppre
ssed this BP and restored levels back to these seen in sham-operated contro
l fish. tPRL(177) and tPRL(188) were also effective in lowering IGFBP-20K l
evels. Levels of the 29-kDa IGFBP (termed IGFBP-29K) increased after hypoph
ysectomy; tGH at all doses and tPRL(177) at the two lower doses further inc
reased these levels. All doses of tGH, tPRL(177), and tPRL(188) significant
ly increased levels of the 32-kDa IGFBP (termed IGFBP-32K). Hypophysectomy
significantly lowered levels of the 40-kDa IGFBP (termed IGFBP-40K) below l
evels seen in the sham-operated controls, tGH treatment significantly raise
d IGFBP-40K levels at all doses examined, but not to the levels seen in int
act tilapia. The 42-kDa IGFBP (termed IGFBP-42K) was not affected by hypoph
ysectomy or hormone replacement. Our data suggest that the novel 20-kDa IGF
BP and the 40-kDa IGFBP species may be similar in function to mammalian IGF
BP-1 and IGPBP-3, respectively. (C) 2000 Academic Press.