Accumulation of Exogenous ⁴⁵Ca after Middle Cerebral Artery Occlusion in Rats

Abstract

The distribution of exogenous ⁴⁵Ca in the focal ischemia rat model (middle cerebral artery occlusion) was studied using ⁴⁵Ca autoradiography. High ⁴⁵Ca accumulations were observed in the frontal cortex and caudate-putamen corresponding with morphological damage shown by HE staining. Regional ⁴⁵Ca concentrations were calculated from the optical density on the ⁴⁵Ca autoradiograms. Rapid uptake of ⁴⁵Ca in the ischemic brain occurred during the first 5 hours, and continued more slowly between 5 and 24 hours after ischemia. The area of ⁴⁵Ca accumulation was also expanded between 5 and 24 hours. An area of low ⁴⁵Ca concentration around the area of high accumulation developed 5 hours after ischemia, which presumably accumulated ⁴⁵Ca between 5 and 24 hours after ischemia. The lower concentration of ⁴⁵Ca in the periphery of ischemia may result from: 1) a decrease in the total amount of calcium due to narrowing of extracellular space accompanied by cytotoxic edema, and 2) delayed accumulation of exogenous ⁴⁵Ca due to reduced clearance of extracellular fluid.