125I-BMIPP and 18F-FDG uptake in a transgenic mouse model of stunned myocardium.

Abstract

Reported metabolic patterns in myocardial stunning are not uniform. We investigated relative myocardial perfusion, glucose and fatty acid uptake using a technetium-99 hexakis-2-methoxyisobutyl-isonitrile (MIBI), fluorine-18 2-fluoro-2-deoxyglucose (FDG) and iodine-125 15-(p-iodo-phenyl)-3(R,S)-methylpentadecanoic acid (BMIPP) mixture, in a recently developed transgenic (TR) mouse model which mimics stunned myocardium. Twenty-seven mice - 14 TR and 13 age-matched wild type controls (C) - were divided into four groups: TR-fed, TR-fasted, C-fed and C-fasted. Animals were sacrificed 2 h after injection, tissue samples counted and percent-injected dose/gram tissue (% id/g) calculated for each radioisotope. Tissues were also Folch extracted and 125I incorporation into the various lipid pools (TG, triglycerides; DG, diglycerides; FFA, free fatty acids; PL, phospholipids) was determined by thin-layer chromatography (TLC). The pooled data for each of the four groups (TR-fed vs C-fed and TR-fed vs C-fasted) showed no differences in myocardial blood flow (% MIBI id/g), glucose uptake (% FDG id/g) or fatty acid uptake (% BMIPP id/g). Only minor differences were observed in the incorporation of 125I-BMIPP into the myocardial TG, DG, FFA and PL lipid pools. However, significantly decreased myocardial FDG uptake was observed in a subset of fasted mice - four out of ten TR-fasted mice (3.4% vs 20.5% id/g) and three out of nine C-fasted mice (5.5% vs 30.6% id/g). The transgenic mouse model of stunned myocardium shows normal myocardial perfusion and overall intact myocardial glucose and myocardial fatty acid uptake as determined with clinically applicable radiolabelled analogues. These data are in line with the hypothesis that the contractile inefficiency in stunned myocardium is not linked to metabolic alterations but is associated with an insufficient chemical to mechanical energy coupling.