Submitted to: International Symposium on Insulin-Like Growth Factors
Publication Type: Abstract Only
Publication Acceptance Date: December 10, 1993
Publication Date: N/A
The effect of continuous vs pulsatile cGH administration on tissue IGF-1 protein and IGF-1 mRNA levels were examined in 8 wk old meat-type chickens. Birds were infused via infusion pumps with either cGH or saline. In both regimes the birds received 123 ug/kg bwt/day. IGF-1 protein concentration (pg/mg protein) were determined by RIA and the relative levels of IGF-1 mRNA by a solution hybridization nuclease protection assay in liver, kidney, spleen, heart, muscle (gastrocnemius and pectoralis major) and growth plate cartilage. Continuous infusion elicited a two fold increase in IGF-1 concentrations in the kidney, while all other tissue concentrations were not altered. Pulsatile infusion caused a two-fold increase in IGF-1 concentrations in the liver, gastrocnemius and pectoralis muscles. IGF-1 levels in other tissues surveyed remained unchanged. With continuous infusion there was a 2-fold increase in the levels of IGF-1 mRNA in the liver and spleen. Kidney and gastrocnemius muscle levels remained unchanged while cardiac and pectoralis muscle mRNA levels decreased 35 and 55% respectively. Pulsatile infusion resulted in a 75% increase in IGF-1 mRNA in the liver and remained unchanged in other tissues. Under both patterns of administration, changes in IGF-1 mRNA did not reflect changes in IGF-1 protein levels. Overall, the correlation between message and protein levels were low in all tissues except for liver under pulsatile infusion, in which IGF-1 levels paralleled changes in IGF-1 mRNA. The results of this study demonstrate that there is a differential tissue response to cGH infusion in local IGF-1 production in the domestic bird.