THE EFFECT ON CREATINE-KINASE RELEASE OF ALTERED CONDITIONS IN THE CA-2+ PARADOX

1. Release of creatine kinase (CK) in the Ca2+ paradox of the Langendorff-perfused rat heart is dependent on the conditions of Ca2+ depletion and Ca2+ repletion. 2. CK release is reduced by raising [Ca2+]o during Ca2+ depletion and progressively increased by extending the Ca2+ free period from 2 to 5 min. 3. CK release is reduced by decreasing the electrochemical gradient for Ca2+ during Ca2+ repletion. 4. The findings are discussed in the light of current hypotheses for the biochemical mechanisms that underlie the Ca2+ paradox.