Myocardial high energy phosphates and function as influenced by di- or trivalent cations and isoproterenol or DBcAMP

Abstract

The effects of Mn++, La+++ and Co++ (2 mM) with and without ISO or DBcAMP were investigated in isolated perfused rat hearts concerning mechanical and metabolic parameters. Mn++ and La+++ produce cardiac arrest accompanied by unchanged content of high energy phosphates. ISO or DBcAMP resp. administered together with these cations do not exhibit characteristic effects. Co++ induces cardiac arrest as well, but in addition severe reduction of high energy phosphate stores and O2-consumption. The effects of Co++ can be partly prevented by administration of ISO and elevated extracellular Ca++ concentration concerning mechanical parameters and oxygen consumption, whereas high energy phosphate stores remain low. The results obtained demonstrated that the Ca++ antagonistic ions studied show the expected metabolic consequences of EC-uncoupling only in the case of Mn++ and La+++. Co++ ions induce in additions to cardiac arrest and low O2-consumption severe reduction of high energy phosphate stores indicating disturbance of respiratory control of mitochondria.

Function and energy metabolism of isolated rat hearts as influenced by Sr++*

“…Thus the immediate substrate of respiration might become rate-limiting and conditions of state 4 and state 3 are left in favour of a state 2 respiration, i.e. But it may be due to a direct but delayed inhibition of NADHoxidation by the respiratory enzymes by Sr ++ which, for instance, is also observed following the application of cobalt (27,53). According to our studies, Sr § is sufficiently capable of replacing Ca § for a short period only in high concentrations and in the presence of isoproterenol.…”