Effect of somatostatin on β-endorphin release in rat experimental chronic inflammation

The aim of the present study was to investigate the effect of somatostatin administration in arthritic rats. Inflammation was induced by daily interplantar injection of 100 mu l of Freund's complete adjuvant into the left hind paw of the rat. Arthritis developed 20 days following the first injection and was stable in the inoculate paw. Arthritic rats were treated interplantarly with somatostatin (5 or 10 mu g) or with indomethacin (100 mu g) daily for 14 days. Inflammatory response was studied at 12 h, 7 and 14 days following drug administration. The effect of somatostatin was determined by local (into popliteal lymph nodes) and systemic production of beta-endorphin. Our results showed that somatostatin treatment significantly increased beta-endorphin levels in the blood and lymphocytes from popliteal lymph nodes. Greater efficiency was seen when 5 mu g instead of 10 mu g of somatostatin was used. A significant decrease of absolute leukocytosis was observed at the 14(th) day following somatostatin administration. Moreover, a significant reduction of plasmatic P-globulins at 12 h and the 7(th) day and of plasmatic alpha 2-globulins at the 14(th) day was observed after the beginning of somatostatin treatment.