Abstract
It is increasingly clear that growth hormone (GH) has growth-promoting effects in fishes, which are mediated in part by the insulin-like growth factor (IGF)-I. Growth-promoting actions of prolactin (PRL) have been reported in higher vertebrates, but are less well established in teleosts. We examined the effects of injecting homologous GH or the two homologous tilapia PRLs (tPRL177 and tPRL188) on the in vitro incorporation of [35S] sulfate (extracellular matrix synthesis) and [3H]thymidine (DNA synthesis) by ceratobranchial cartilage explants and on IGF-I mRNA levels in tilapia liver. Tilapia GH (tGH) and tPRL177 stimulated sulfate uptake at the highest doses examined. Thymidine incorporation was stimulated by tPRL177. tPRL188 was without these effects. Consistent with its somatotropic actions, tGH elevated IGF-I mRNA levels in the liver. tPRL177 also elevated liver IGF-I levels. Consistent with the previously described osmoregulatory actions of GH and PRL in teleosts, we observed that tGH elevated and tPRL177 and tPRL188 lowered levels of gill Na+,K+- ATPase activity. High-affinity, low-capacity binding sites for tGH in the tilapia liver were identified. tPRL177 binds with lower affinity than tGH to these sites but can displace 125I-labeled tGH from its receptor. The ability of tPRL177 to displace tGH was similar to that of ovine GH. tPRL188 did not displace 125I-labeled tGH binding. Collectively, this work suggests that tPRL177 may possess somatotropic actions similar to tGH, but only in freshwater tilapia where tPRL177 levels are sufficiently high for it to act as a competitive ligand for GH receptors.
| Original language | English |
|---|---|
| Pages (from-to) | 2068-2072 |
| Number of pages | 5 |
| Journal | Proceedings of the National Academy of Sciences of the United States of America |
| Volume | 94 |
| Issue number | 5 |
| DOIs | |
| Publication status | Published - Mar 4 1997 |
| Externally published | Yes |
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Keywords
- growth promotion
- insulin-like growth factor
ASJC Scopus subject areas
- Genetics
- General
Cite this
Somatotropic actions of the homologous growth hormone and prolactins in the euryhaline teleost, the tilapia, Oreochromis mossambicus. / Shepherd, Brian S.; Sakamoto, Tatsuya; Nishioka, Richard S.; Richman, Nurney H.; Mori, Ikue; Madsen, Stephen S.; Chen, Thomas T.; Hirano, Tetsuya; Bern, Howard A.; Grau, E. Gordon.
In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 94, No. 5, 04.03.1997, p. 2068-2072.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Somatotropic actions of the homologous growth hormone and prolactins in the euryhaline teleost, the tilapia, Oreochromis mossambicus
AU - Shepherd, Brian S.
AU - Sakamoto, Tatsuya
AU - Nishioka, Richard S.
AU - Richman, Nurney H.
AU - Mori, Ikue
AU - Madsen, Stephen S.
AU - Chen, Thomas T.
AU - Hirano, Tetsuya
AU - Bern, Howard A.
AU - Grau, E. Gordon
PY - 1997/3/4
Y1 - 1997/3/4
N2 - It is increasingly clear that growth hormone (GH) has growth-promoting effects in fishes, which are mediated in part by the insulin-like growth factor (IGF)-I. Growth-promoting actions of prolactin (PRL) have been reported in higher vertebrates, but are less well established in teleosts. We examined the effects of injecting homologous GH or the two homologous tilapia PRLs (tPRL177 and tPRL188) on the in vitro incorporation of [35S] sulfate (extracellular matrix synthesis) and [3H]thymidine (DNA synthesis) by ceratobranchial cartilage explants and on IGF-I mRNA levels in tilapia liver. Tilapia GH (tGH) and tPRL177 stimulated sulfate uptake at the highest doses examined. Thymidine incorporation was stimulated by tPRL177. tPRL188 was without these effects. Consistent with its somatotropic actions, tGH elevated IGF-I mRNA levels in the liver. tPRL177 also elevated liver IGF-I levels. Consistent with the previously described osmoregulatory actions of GH and PRL in teleosts, we observed that tGH elevated and tPRL177 and tPRL188 lowered levels of gill Na+,K+- ATPase activity. High-affinity, low-capacity binding sites for tGH in the tilapia liver were identified. tPRL177 binds with lower affinity than tGH to these sites but can displace 125I-labeled tGH from its receptor. The ability of tPRL177 to displace tGH was similar to that of ovine GH. tPRL188 did not displace 125I-labeled tGH binding. Collectively, this work suggests that tPRL177 may possess somatotropic actions similar to tGH, but only in freshwater tilapia where tPRL177 levels are sufficiently high for it to act as a competitive ligand for GH receptors.
AB - It is increasingly clear that growth hormone (GH) has growth-promoting effects in fishes, which are mediated in part by the insulin-like growth factor (IGF)-I. Growth-promoting actions of prolactin (PRL) have been reported in higher vertebrates, but are less well established in teleosts. We examined the effects of injecting homologous GH or the two homologous tilapia PRLs (tPRL177 and tPRL188) on the in vitro incorporation of [35S] sulfate (extracellular matrix synthesis) and [3H]thymidine (DNA synthesis) by ceratobranchial cartilage explants and on IGF-I mRNA levels in tilapia liver. Tilapia GH (tGH) and tPRL177 stimulated sulfate uptake at the highest doses examined. Thymidine incorporation was stimulated by tPRL177. tPRL188 was without these effects. Consistent with its somatotropic actions, tGH elevated IGF-I mRNA levels in the liver. tPRL177 also elevated liver IGF-I levels. Consistent with the previously described osmoregulatory actions of GH and PRL in teleosts, we observed that tGH elevated and tPRL177 and tPRL188 lowered levels of gill Na+,K+- ATPase activity. High-affinity, low-capacity binding sites for tGH in the tilapia liver were identified. tPRL177 binds with lower affinity than tGH to these sites but can displace 125I-labeled tGH from its receptor. The ability of tPRL177 to displace tGH was similar to that of ovine GH. tPRL188 did not displace 125I-labeled tGH binding. Collectively, this work suggests that tPRL177 may possess somatotropic actions similar to tGH, but only in freshwater tilapia where tPRL177 levels are sufficiently high for it to act as a competitive ligand for GH receptors.
KW - growth promotion
KW - insulin-like growth factor
UR - http://www.scopus.com/inward/record.url?scp=12644267270&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=12644267270&partnerID=8YFLogxK
U2 - 10.1073/pnas.94.5.2068
DO - 10.1073/pnas.94.5.2068
M3 - Article
C2 - 9050906
AN - SCOPUS:12644267270
VL - 94
SP - 2068
EP - 2072
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
SN - 0027-8424
IS - 5
ER -