Submitted to: International Symposium on Insulin-Like Growth Factors
Publication Type: Abstract Only
Publication Acceptance Date: December 10, 1993
Publication Date: N/A
The purpose of this study was to investigate organ distribution and plasma clearance of labelled chicken IGF-1 (cIGF-1) and IGF-2 (cIGF-2) in the broiler chicken. Both growth factors were radiolabelled to a specific activity of 70 uCi/ug and injected into male chicks via a jugular cannula at a concentration of 40 uCi/kg bwt. Plasma samples were drawn at 7.5, 15, 30, 60 and 120 min post-infusion and subjected to size exclusion chromatography. Four birds were sacrificed at 15 min and 4 at 120 min post-infusion and selected tissues removed and the radioactivity counted. With both growth factors, radioactivity appeared in the kidneys to a greater extent than in other organs. The amount of radioactivity found in the various organs in rank order were, kidney>heart>liver>testis> intestine>pancreas>cartilage>bone>bursa>gizzard>leg muscle>breast muscle>brain. The only organ in which the uptake of labelled cIGF-2 exceeded that of cIGF-1 was the liver. In all other tissues, cIGF-1 uptake (cpm/mg tissue) exceeded that of a cIGF-2. The half-lives for cIGF-1 and cIGF-2 were calculated to be different (p<.05), 39.9 and 30.2 min, respectively. Labelled cIGF-1 in plasma was associated with three peaks of radioactivity (150, 40 kDA and free cIGF-1). At 7.5 min a majority of the radioactivity was associated with the 40 kDa fraction. With time, the proportion of radioactivity in the three components changed, as at 120 min, most of the activity remained in the 150 complex, with little activity in 40 kDa component or as free IGF-1. This study demonstrates that in the bird, IGFs are rapidly taken up by tissues and that the IGFs are associated in plasma with binding proteins in a manner similar to mammals.