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 μl 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 μg) or with indomethacin (100 μg) 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 β-endorphin. Our results showed that somatostatin treatment significantly increased β- endorphin levels in the blood and lymphocytes from popliteal lymph nodes. Greater efficiency was seen when 5 μg instead of 10 μg of somatostatin was used. A significant decrease of absolute leukocytosis was observed at the 14th day following somatostatin administration. Moreover, a significant reduction of plasmatic β-globulins at 12 h and the 7th day and of plasmatic α2-globulins at the 14th day was observed after the beginning of somatostatin treatment.