Objective: To observe the effects of exogenous adrenomedullin (ADM) on endogenous expression of ADM in the kidney and hypothalamus of rats early after mechanical renal trauma.
Methods: Adult Wistar rats were randomized into 4 groups (n=32), namely the control group, renal impact trauma group, preventive ADM injection group, and therapeutic ADM injection group. In the latter two groups, ADM (0.1 nmol/kg) was administrated by intraperitoneal injection 10 min before and 10 min after renal trauma. The rats were executed at 1, 6, 12, and 24 h after the trauma to examine the expression of ADM in the kidney and hypothalamus.
Results: In preventive ADM injection group, the renal expression of ADM increased significantly at 1 h after the trauma (P<0.05) and tended to further increase with time till 24 h when its expression recovered the normal level. In the therapeutic ADM injection group, strong renal ADM positivity was found at 1 and 6 h after the injury (P<0.05) followed by gradual decrease till recovering the normal level at 24 h. Low renal ADM expression was detected, which was the strongest at 1 and 12 h (P<0.05) and became normal at 24 h. The time course of ADM expression in the hypothalamus was similar to that in the kidney in the therapeutic ADM injection group, and in the preventive injection group, the strongest ADM expression in the hypothalamus occurred at 6 and 24 h, and the lowest expression occurred at 12 h (P<0.05). The trauma group showed significantly decreased ADM expression in the hypothalamus compared with the control group (P<0.05).
Conclusion: The hypothalamic ADM expression can upregulate renal ADM expression. ADM maintains the relative stability of the internal environment and physiological activity by local and systemic positive and negative feedback mechanisms.