ACCELERATION OF POSTISCHEMIC ADENINE NUCLEOTIDE SYNTHESIS DURING 3 H OF REPERFUSION IN THE DOG. COMPARISON OF ADENOSINE, AICAR (5-Amino-4-Imidazole-Carboxamide-Riboside) AND RIBOSE M. Mauser, H.-M. Hoffmeister, Ch. Nienaber, W. Schaper Postischemic reperfused myocardium needs more than three days to replenish decreased adenine nuoleotide (AN) pools. The effect of adenosine (Ado), AICAR (physiological precursor of the AN-de-novo-synthesis) or ribose as substrates of AN resyntheses was studied in 27 dogs. Ado and AICAR need only one resp. two mole (m) of ATP to be converted to AMP instead of 7 m ATP to form AMP from ribose. A sidebranch of the circumflex coronary artery (CX) was occluded for 45 min and then reperfused for 3 h together with intracoronary infusion of one of the substrates (3 mM/h) into the CX. Transmural needle biopsies obtained at the end of ischemia and reperfusion were chromatographically (HPLC) analysed for nucleotides, nucleosides and CP. Ado and AICAR were taken up by the cell, phosphorylated to AMP resp. AICAR-MP and transformed to ATP as shown by 3H-Ado and 3H-AICAR incorporation studies. Ado and AICAR caused a similar significant increase of ATP from postischemio 50 % to 75 % of control levels which means a myocardial AN recovery rate of 4.4 nmols ATP/min/g WW. Ribose or reperfusion without additional substrate had no effect within the first 3 h of reperfusion.