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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: OBJECTIVE, METHODS, RESULTS. Meshes: Animals, Arthritis, Experimental, Growth Hormone, Insulin-Like Growth Factor Binding Protein 3, Insulin-Like Growth Factor Binding Protein 5, Insulin-Like Growth Factor Binding Proteins, Insulin-Like Growth Factor I, Male, Muscle, Skeletal, Rats, Rats, Wistar.
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Does short-term growth hormone or IGF-I administration improve the IGF-IGFBP system in arthritic rats? Context: Adjuvant-induced arthritis is an experimental model of rheumatoid arthritis that inhibits the GH-IGF-I axis and decreases body weight gain and muscle mass. Although chronic GH or IGF-I treatment increases body weight gain in arthritic rats, muscle resistance to GH and IGF-I is a very common complication in inflammatory diseases. In this study we examine the effect of short-term administration of rhGH and rhIGF-I on liver and muscle IGF-I, IGFBP-3 and -5 as well as on the ubiquitin-ligases MuRF1 and atrogin-1 in the muscle of arthritic rats. Arthritis was induced in adult male Wistar rats by an intradermal injection of 4 mg of Freund's adjuvant. Fifteen days after adjuvant injection, 300 μg/kg of rhGH or 200 μg/kg of rhIGF or saline was administrated 18 and 3h before decapitation. A pair-fed group injected with saline was included in order to discard a possible effect of decreased food intake. Gene expression of IGF-I, GHR, IGFBP-3, IGFBP-5, atrogin-1 and MuRF1 were quantified using RT-PCR. In serum, IGF-I was measured by radioimmunoassay (RIA) and IGFBP-3 by ligand blot. Arthritis decreased serum IGF-I and IGF mRNA in liver (P<0.05), but not in skeletal muscle. In arthritic rats, rhGH increased serum IGF-I and liver IGF-I mRNA similar to the levels of pair-fed rats. Arthritis increased atrogin-1, MuRF1, IGFBP-3 and IGFBP-5 mRNA in muscle (P<0.01). IGFBP-3 mRNA was downregulated by rhIGF-I, but not by rhGH, administration in control and arthritic rats (P<0.05). Administration of rhGH and rhIGF-I increased IGFBP-5 in the gastrocnemius of arthritic rats.
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Short-term rhGH and rhIGF-I administration was found to increase muscle IGFBP-5 mRNA, whereas only rhIGF-I administration decreased muscle IGFBP-3 mRNA in control and arthritic rats. These data suggest that arthritis does not induce GH or IGF-I resistance in skeletal muscle. Final Decision: yes