Effects of fasting on growth hormone/insulin-like growth factor I axis in the tilapia, Oreochromis mossambicus.
Effects of fasting on the growth hormone (GH)-insulin-like growth factor I (IGF-I) axis were examined in the tilapia (Oreochromis mossambicus) acclimated to fresh water. Fasting for 2 weeks resulted in significant reductions in body weight, specific growth rate and hepatosomatic index in both males and females. Significant reductions in specific growth rates were observed after 1 and 2 weeks in both sexes, although the decrease in body weight was not significant in the female. A significant reduction was also seen in the condition factor of females after 2 weeks. No change was seen in the gonadosomatic index in either sex. Two weeks of fasting also produced a significant reduction in plasma IGF-I but not in plasma GH, prolactin (PRL(188)) or cortisol. Significant reductions in the hepatic IGF-I mRNA were seen in both sexes. On the other hand, a significant increase was observed in cortisol receptor mRNA in the female liver. Plasma IGF-I levels were correlated significantly with specific growth rate, condition factor and hepatosomatic index, indicating that plasma IGF-I is a good indicator of growth in the tilapia. No change was seen in plasma glucose or osmolality after 2 weeks of fasting. During fasting, tilapia appears to convert metabolic energy from growth to basal metabolism including maintenance of ion and water balance.
Uchida
K
K
Department of Zoology and Hawaii Institute of Marine Biology, University of Hawaii, 96744, Kaneohe, HI, USA.
Kajimura
S
S
Riley
L G
LG
Hirano
T
T
Aida
K
K
Grau
E G
EG
D000818:Animals; D005215:Fasting / Q000378:metabolism*; D005260:Female; D005618:Fresh Water; D013006:Growth Hormone / Q000097:blood / Q000378:metabolism*; D006854:Hydrocortisone / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism*; D008099:Liver / Q000378:metabolism; D008297:Male; D010446:Peptide Fragments / Q000097:blood; D011388:Prolactin / Q000097:blood; D012333:RNA, Messenger / Q000378:metabolism; D011965:Receptors, Glucocorticoid / Q000235:genetics / Q000378:metabolism; D017210:Tilapia / Q000254:growth & development / Q000378:metabolism*
D010446:Peptide Fragments; D012333:RNA, Messenger; D011965:Receptors, Glucocorticoid; C029360:hydrocortisone receptor; D007334:Insulin-Like Growth Factor I; D011388:Prolactin; D013006:Growth Hormone; D006854:Hydrocortisone