ObjectiveTo investigate the protective effect of exogenous insulin on relative adrenal insufficiency (RAI) in rats with severe acute pancreatitis (SAP).MethodsEighty SPF SD rats were randomly divided into 5 groups (n=16): sham operation (SO) group, SAP group, low-dose insulin intervention (low-dose) group (0.05 U/100 g body weight), medium-dose insulin intervention (medium-dose) group (0.1 U/100 g body weight), and high-dose insulin intervention (high-dose) group (0.2 U/100 g body weight). The five groups were randomly divided into two subgroups: cosyntropin stimulation test (CST) subgroup and non-CST subgroup. SAP model was established by retrograde injection of 5% sodium taurocholate into biliopancreatic duct. The rats were sacrificed 3 hours after the establishment of SAP model. The levels of amylase (AMY), alanine aminotransferase (ALT), aspartate aminotransferase (AST), urea (Ur) and creatinine (Cr) were detected by automatic biochemical analyzer. The serum levels of tumor necrosis factor-α (TNF-α) and corticosterone (Cor) were detected by ELISA kit. The pathological changes of pancreas and adrenal gland were observed under light microscope. The lipid content of adrenal gland was observed by oil red O staining.ResultsCompared with the SO group, the serum levels of Amy, ALT, AST, Ur, Cr, TNF-α and Cor in the SAP group were significantly increased (P<0.05), typical pathological damages occurred in pancreas and adrenal gland, and pathological scores were significantly increased (P<0.05). Compared with the SAP group, the levels of AMY, ALT, AST, Ur, Cr, TNF-α and Cor in the low-dose group were not significantly changed (P>0.05); the levels of AMY, ALT, AST, Ur, Cr and TNF-α in the medium-dose group and the high-dose group were significantly decreased (P<0.05), and Cor levels were significantly increased (P<0.05). Compared with the low-dose group, AMY, ALT, AST, Cr, TNF-α in the medium-dose group and the high-dose group were significantly decreased (P<0.05), Cor level were significantly increased (P<0.05), Ur level had no significant change. There were no significant difference in AMY, ALT, AST, Ur, Cr, TNF-α and Cor levels between the medium-dose group and the high-dose group (P>0.05). After CST intervention, there were no significant change in serum Cor levels in the SAP group and the low-dose group (P>0.05), but the serum Cor levels in the SO group, the medium-dose group and the high-dose group were significantly increased (P<0.05).ConclusionAppropriate dose of exogenous insulin can improve SAP related adrenal injury and RAI, but the specific mechanism still needs further study.