Effects of mannitol and glycerol on cerebral energy metabolism in gerbils.

Abstract

To evaluate the effects of infusion with hyperosmolar solutions, mannitol and glycerol on the recovery of cerebral energy metabolism during ischemia and reperfusion in the gerbil brain. Sequential changes in cerebral energy metabolism following 90-min ischemia and up to 8 h after reperfusion were measured in 15 gerbils using 31P nuclear magnetic resonance (NMR) spectroscopy after 60-min infusion of 10% glycerol (0.5 g/kg; n=5), or 20% mannitol (1.0 g/kg; n=5), and compared with those gerbils receiving with saline (n=5). Gerbils were anesthetized by intraperitoneal injection of pentobarbital. Forebrain ischemia was induced by clipping of bilateral common carotid arteries for 90 min and reperfused. NMR spectroscopy was measured by a 6.34-Tesla JEOL spectrometer, before administration, 2, 4, 6, and 8 h after 90-min ischemia and reperfusion. Areas of inorganic phosphate (Pi), phosphocreatine (PCr), and beta-ATP peaks were measured to calculate parameters of cerebral energy metabolism, i.e., PCr/Pi and beta-ATP/Pi ratios. Intracellular pH (pHi) was calculated from chemical shifts of Pi relative to PCr. PHi was higher in the mannitol group than in the glycerol and saline groups (P<0.05) 2 h after reperfusion. PCr/Pi ratio was higher 2, 4, and 8 h after reperfusion (P<0.01, P<0.05, P<0.01) in the mannitol group; and 6 h after reperfusion (P<0.05) in the glycerol group; than in the saline group. Beta-ATP/Pi ratio was higher 2 and 8 h after reperfusion (P<0.05) in the glycerol group; and 2 h after reperfusion (P<0.01) in the mannitol group, than in the saline group. The mannitol group had improved pHi higher than the glycerol group 2 h after reperfusion (P<0.05), while the glycerol group had improved beta-ATP/Pi ratio higher than the mannitol group 6 h after reperfusion (P<0.05). Both mannitol and glycerol groups had improved parameters of cerebral energy metabolism during ischemia and up to 8 h after reperfusion in the gerbil brain.