Change in Serum Concentration of Magnesium and Calcium Ions Following Moderate Diffuse Axonal Injury in Rats: Preliminary Study

ABSTRACT

OBJECTIVE: Traumatic brain injury has been shown to result in a decrease of the brain-free magnesium concentration that is associated with the development of neurologic deficits. However, changes in free magnesium homeostasis have not been characterized in other fluid compartments. We examine the ionized serum magnesium(Mg2+) and ionized serum calcium(Ca2+) in the moderate diffuse axonal injury of rat model. METHODS: We designed a study to determine whether ionized serum magnesium(Mg2+) and / or ionized serum calcium(Ca2+) levels correlate with moderate diffuse axonal injury(mDAI). A new ion-selective electrode was used to determine Mg2+ and Ca2+ level in the serum, prior to and following weight-drop induced mDAI. RESULTS: Serum Mg2+ remained significantly depressed to about 76% of preinjury values for 3 hours (0.73+/-0.01 mg/dL, 0.79+/-0.03 mg/dL, 0.84+/-0.03 mg/dL at 1, 2, 3 hours after trauma, respectively) compared to control group (1.07+/-0.03 mg/dL, p<0.05), but not in total serum magnesium(tMg). Mg2+/ tMg was shown a significant decrease for first 3 hours (49%, 53.4%, 56.4% at 1, 2, 3 hours after trauma respectively) compared to control group (70.9%, p<0.05). Head trauma resulted in small decrease of Ca2+, but there was a significant increase in the amount of Ca2+/ Mg2+(mean value in control group: in injured group for 3 hours after trauma = 4.65+/-0.012: 5.71+/-0.015, p<0.05). Apoptotic change was shown at 3 hours after mDAI and apoptotic index(AI) was significantly increased at 12 and 24 hours after trauma (54.8+/-1.7, 51.5+/-3.2 at 12, 24 hours, p<0.05). CONCLUSION: These findings suggest that the early decline in serum Mg2+ and increase in the amount of Ca2+/ Mg2+ following brain trauma may be a critical factor in the development of irreVersible tissue injury and early treatment with magnesium salt may be effective in histological changes following experimental traumatic brain injury in the rat.