IGF-I and branchial IGF receptor expression and localization during salinity acclimation in striped bass.
The initial response of the IGF-I system and the expression and cellular localization of IGF type-I receptor (IGF-IR) were studied in the gill of a euryhaline teleost during salinity acclimation. Exposure of striped bass (Morone saxatilis) to hyperosmotic and hypoosmotic challenges induced small, transitory (<24 h) deflections in hydromineral balance. Transfer from freshwater (FW) to seawater (SW) induced an initial decrease in plasma IGF-I levels after 24 h in both fed and fasted fish. There was an overall decrease in liver IGF-I mRNA levels after SW transfer, suggesting that decreased plasma levels may be due to a decline in hepatic IGF-I synthesis. No changes were observed in gill IGF-I mRNA, but SW transfer induced an increase in gill IGF-IR mRNA after 24 h. Transfer from SW to FW induced an increase in plasma IGF-I levels in fasted fish. In fed fish, no significant changes were observed in either plasma IGF-I, liver, or gill IGF-I mRNA, or gill IGF-IR mRNA levels. In a separate experiment, FW-acclimated fish were injected with saline or IGF-I prior to a 24-h SW challenge. Rapid regain of osmotic balance following SW transfer was hindered by IGF-I. Immunohistochemistry revealed for the first time in teleosts that IGF-IR and Na(+)-K(+)-ATPase are localized in putative chloride cells at the base of the lamellae, identifying these cells in the gill as a target for IGF-I and IGF-II. Overall the data suggest a hyperosmoregulatory role of IGF-I in this species.
Tipsmark
Christian Kølbaek
CK
Department of Zoology, North Carolina State University, Raleigh, North Carolina, USA. ckt@biology.sdu.dk
Luckenbach
John Adam
JA
Madsen
Steffen Søndergaard
SS
Borski
Russell John
RJ
D000064:Acclimatization / Q000502:physiology*; D000818:Animals; D001492:Bass / Q000378:metabolism*; D001786:Blood Glucose / Q000378:metabolism; D001834:Body Water / Q000378:metabolism; D018076:DNA, Complementary / Q000096:biosynthesis; D005260:Female; D005880:Gills / Q000378:metabolism*; D006854:Hydrocortisone / Q000097:blood; D007150:Immunohistochemistry; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis*; D008297:Male; D009994:Osmolar Concentration; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D017526:Receptor, IGF Type 1 / Q000096:biosynthesis*; D012623:Seawater; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D001786:Blood Glucose; D018076:DNA, Complementary; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1; D000254:Sodium-Potassium-Exchanging ATPase; D006854:Hydrocortisone