A radioisotopic method for the simultaneous quantitation of regional cerebral blood flow and glucose utilization in small dissected samples: validation studies and values in the nitrous oxide-anesthetized rat.
A method is described for the simultaneous determination of the rates of regional cerebral blood flow (rCBF) and regional cerebral glucose utilization (rCMRgl) in 6-7 mg brain samples dissected from multiple areas of interest. The method utilizes [131I]iodoantipyrine ([131I]IAP) to measure rCBF by indicator fractionation, and [14C]2-deoxyglucose to measure rCMRgl. [131I]IAP was synthesized with specific activity exceeding 350 Ci/mmol and radiochemical purity greater than 99.5% by the radioiodination of antipyrine with Na131I. A triple-counting strategy was developed to quantitate 14C activity of the dissected brain samples in the presence of 131I. The factors contributing to the propagated error of the double-label separation strategy were defined and optimal assay parameters were determined. The separation strategy was validated by measuring rCBF simultaneously with both [131I]IAP (x) and [14C]IAP (y) in a series of rats. The equation of the regression line was y = 1.025 x -0.065 (correlation coefficient 0.985), denoting excellent agreement. In another series of 5 normocapnic rats anesthetized with nitrous oxide, rCBF and rCMRgl were measured simultaneously. In individual animals, the rates of rCBF within 14-16 brain areas were closely coupled to their respective rates of glucose metabolism. For the group data, the linear regression equation relating rCBF (y) to rCMRgl (x) was y = 1.76 x + 0.13 (correlation coefficient 0.93, P less than 0.001). These studies provide direct evidence, based upon data obtained in the same brain, of a close coupling of regional metabolic rate and blood flow.
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism*; D001921:Brain / Q000000981:diagnostic imaging*; D002250:Carbon Radioisotopes; D002560:Cerebrovascular Circulation; D007457:Iodine Radioisotopes; D008297:Male; D011877:Radionuclide Imaging; D051381:Rats; D011919:Rats, Inbred Strains; D012039:Regional Blood Flow
D001786:Blood Glucose; D002250:Carbon Radioisotopes; D007457:Iodine Radioisotopes