Effects of Administration of an Anti-sense Oligonucleotide to Insulin-like Growth Factor-Binding Protein-3 (IGFBP-3) mRNA on Expression of Humoral IGF System Components and Organ Growth in Growing Rats

Insulin-like growth factor-binding protein-3 (IGFBP-3) is the major plasma carrier and reservoir of IGF-1 which mediates most of the growth-promoting action of growth hormone. The present study was undertaken to examine the effect of administration of a phosphorothioate anti-sense deoxyribouncleotide (AODN; 5'-CATGGCGCTGGCGGAGGGC-3') targeted to a 5'-untranslated region of IGFBP-3 mRNA in growing rats. After confirming the effectiveness of the AODN in reducing the IGFBP-3 mRNA abundance in C6 rat glial cells in culture, male Sprague-Dawley rats weighing approximately 200 g were intra-peritoneally injected with 0.08-, 0.8-, 8-㎎ AODN or 8-㎎ random ODN per kg body weight every 12 h for 3 days. Blood samples were taken from the tail vein on d-1, 0, 1 and 3 of the experiment. Internal organs were excised and weighed at sacrifice following the last blood sampling. Hepatic IGFBP-3 mRNA abundance analyzed by Northern blotting, as well as plasma levels of IGFBP-3 and other IGFBPs resolved by Western ligand blotting, did not differ among the four groups. Plasma IGF-1 concentrations tended to increase with increasing doses of the AODN, with 0.09 of p-value for the effect of the treatment. Interestingly, weight of spleen, a most IGF-1-responsive organ, exhibited an identical trend with respect to IGF-1 concentration, whereas weights of liver, lung, kidney and heart had no relation to the plasma variable. In summary, the present AODN is judged to be minimally effective in blocking IGFBP-3 translation. Further studies are therefore necessary to find a more effective AODN and also to determine if blood IGF-1 concentration and spleen growth have any relation to IGFBP-3 expression.