SUPERIORITY OF ACID EXTRACTABLE GLYCOGEN FOR DETECTION OF METABOLIC CHANGES DURING MYOCARDIAL-ISCHEMIA

Metabolic Changes During 11Iyocardial Ischaemia. lournal of MoIecular and CelIular Cardiology (1995) 27, 1325-1332. Various methods for extr action and isolation of myocardial glycogen show different yields and identify different glycogen subsets. The aim of the present study was to identify a glycogen fraction exposed to changes during myocardial i schaemia. Endomyocardial biopsies from 10 pigs were sampled before car dioplegia, after cardioplegic arrest, and after reperfusion. Glycogen yields were compared following five extraction procedures: (1) hot alk aline tissue digestion, (2) homogenization in perchloric acid and subs equent determination in homogenate, (3) homogenization in perchloric a cid and subsequent determination in supernatant, (4) homogenization in perchloric acid and subsequent determination in the precipitate redis solved in hot alkaline and (5) homogenization in homogenisation buffer with lysating capacity. Glycogen was isolated on filter-paper and det ermined enzymatically. Hot alkaline tissue digestion yielded the highe st glycogen amounts (63.5 +/- 18.3 nmol/mg wet weight). Glycogen yield s in perchloric homogenate and supernatant were 51%, perchloric precip itate 47%, and buffer 30% of these obtained with hot alkaline. Glycoge n yields in hot alkaline were comparable to the sum of those obtained in perchloric supernatant (''acid extractable glycogen'') and redissol ved precipitate (''heavily extracted glycogen'') confirming that glyco gen yields obtained with hot alkaline digestion represent ''total glyc ogen''. Acid extractable glycogen showed superior analytical character istics compared with the other methods. Acid extractable glycogen demo nstrated a consistent decrease during ischaemia whereas total glycogen and glycogen extracted in homogenization buffer tended to decrease. G lycogen in perchloric precipitate remained unchanged during iscbaemia. These findings support a revival of the concept that tissue contains two forms of glycogen. Decreases in myocardial glycogen content during myocardial ischaemia are best observed with acid extractable glycogen .