Ultrastructural observations on the effects of different substrates on ischaemic contracture in global subtotal ischaemia in the rat heart.
Ultrastructural morphology was examined in myocardia perfused with different substrates, following the hypothesis that ultrastructural changes or differences would indicate the mechanism of early ischaemic contracture. Substrates used were glucose, acetate and no substrate (substrate-free). Isolated rat hearts were subjected to global low flow ischaemia followed by perfusion fixation at either no contracture, early contracture (5%) or full contracture (100%). Total tissue adenosine triphosphate (ATP) levels were analysed from myocardia of each group. Glucose perfused myocardia did not develop contracture for at least 30 minutes and maintained ultrastructural and ATP normality. Substrate-free and acetate perfused myocardia developed contracture after 10-12 minutes of ischaemia at which time myofibrillar morphology was altered within small sparse foci of developing mild oedema with contracture and hyperextension of myofibrils. ATP levels were normal. At full ischaemic contracture, both substrate-free and acetate perfused myocardia showed severe mitochondrial damage, oedema, myofibrillar contracture and hyperextension with accompanying distortion and swelling of the sarcoplasmic reticulum.
van der Merwe
E
E
MRC Research Institute for Medical Biophysics, Tygerberg, Republic of South Africa.
Harper
I S
IS
Owen
P
P
Lochner
A
A
Wynchank
S
S
Opie
L H
LH
D000818:Animals; D003327:Coronary Disease / Q000473:pathology* / Q000503:physiopathology; D006321:Heart / Q000503:physiopathology; D066298:In Vitro Techniques; D008854:Microscopy, Electron; D009200:Myocardial Contraction; D009206:Myocardium / Q000648:ultrastructure*; D051381:Rats