Focal expression of insulin-like growth factor I in rat kidney collecting duct.
To address the question of insulin-like growth factor (IGF) I localization and synthesis in kidney, we used two complementary experimental approaches: immunohistochemistry of fixed paraffin-embedded rat kidney sections; and measurement of IGF I mRNA in isolated components of the rat nephron, using a highly sensitive and specific solution hybridization assay. Immunostainable IGF I was localized exclusively to principal cells of cortical and medullary collecting ducts. Administration of growth hormone to hypophysectomized rats for 8 d resulted in enhanced immunohistochemical staining of IGF I within collecting ducts, but no detectable IGF I in other portions of the nephron. The abundance of IGF I mRNA was 7-12-fold higher in isolated papillary collecting ducts than in proximal tubules or glomeruli, and was enriched 10-fold compared with whole kidney. Our data demonstrate colocalization of IGF I and IGF I mRNA in the collecting duct, consistent with focal expression of the IGF I gene at this site.
Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110.
J D
JD
Bortz
P
P
Rotwein
D
D
DeVol
P J
PJ
Bechtel
V A
VA
Hansen
M R
MR
Hammerman
D000818:Animals; D001345:Autoradiography; D001835:Body Weight / Q000187:drug effects; D005260:Female; D006133:Growth Substances / Q000494:pharmacology; D007150:Immunohistochemistry; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics; D007668:Kidney / Q000032:analysis / Q000187:drug effects / Q000254:growth & development; D007684:Kidney Tubules / Q000378:metabolism*; D007685:Kidney Tubules, Collecting / Q000032:analysis / Q000378:metabolism*; D008297:Male; D009693:Nucleic Acid Hybridization; D009929:Organ Size / Q000187:drug effects; D011388:Prolactin / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D011919:Rats, Inbred Strains; D013002:Somatomedins / Q000096:biosynthesis*
D006133:Growth Substances; D012333:RNA, Messenger; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D011388:Prolactin