X-RAY-DIFFRACTION STUDIES OF WHOLE RAT-HEART DURING ANOXIC PERFUSION

Equatorial x-ray reflections were recorded from the ventricular region of whole rat heart, during the transition from normoxia to anoxia. Th e intensity ratio of the 1,0 and 1,1 equatorial reflections (I-1,I-0 / I-1,I-1) was 2.96 during normoxic perfusion, decreasing to 0.37 after 115 minutes of anoxic perfusion and closely parallel those reported be tween partially dissected relaxed and rigor vertebrate heart muscle (1 ,2). The peak positions of these reflections both increased by ca. 5% during anoxic perfusion indicative of a lateral expansion in the sarco mere filament lattice. These results indicate that the process of anox ia leads to the condition of rigor in which the majority of the myosin cross-bridges bind to the thin filament. Using this technique global changes in whole heart structure can be studied, and due to the ease o f perfusion of the heart, biochemical and physiological problems may b e investigated in relation to the structure of the heart as a whole. T his may be of clinical interest, particularly in terms of investigatio ns into organ preservation and transplantation. This is believed to be the first occasion where intact muscular organs have been studied in this way. (C) 1994 Academic Press, Inc.