Biomedical subjects

S Soboll

Publications and source records attributed to S Soboll.

57 records · Page 4Linked to original sources

PubMedDate not supplied

Evidence that mitochondrial phosphate is visible in 31P NMR spectra of isolated, perfused rat hearts.

We have previously found (P. B. Garlick, T. R. Brown, R. H. Sullivan and K. Ugurbil, J. Mol. Cell Cardiol. 15, 855-858 (1983)) that two peaks could be observed in the phosphate region of NMR spectra of isolated, perfused rat hearts. Upon valinomycin treatment, an increase in the peak at 2.8 ppm in the phosphate region (phosphocreatine set at -2.52 ppm) had been observed. We have now confirmed our hypothesis that this peak originates from the mitochondrial phosphate by: (i) determination of myocardial mitochondrial phosphate contents using density gradient centrifugation in non-aqueous solvents; and (ii) quantitative electron microscopy of the heart tissue. Thus, we conclude that mitochondrial and cytosolic phosphate can be distinguished from each other in 31P NMR spectra of isolated, perfused rat hearts.

Adenosine Triphosphate↗

PubMedDate not supplied

Influence of 2,3-butanedione monoxime on heart energy metabolism.

The influence of 2,3-butanedione monoxime (BDM) on function and subcellular energy status in isolated perfused guinea pig hearts was examined during ischemia and reperfusion. For this purpose the mitochondrial and extramitochondrial contents of ATP, ADP, creatine phosphate (CrP) and creatine (Cr) were determined after fractionation of freeze-clamped heart tissue in non-aqueous solvents. Furthermore, the inhibitory action of this compound on isolated cardiac mitochondria and the actomyosin-ATPase was studied. BDM in the millimolar range inhibited both the actomyosin-ATPase in skinned-fibers (IC50 22 mM) and the electron transport chain in isolated mitochondria (IC50 28 mM). In normoxia at 35 degrees C the contractile function of isolated guinea pig hearts was completely inhibited and oxygen consumption was markedly reduced (-60%) by 30 mM BDM. The mitochondrial and extramitochondrial contents of adenine nucleotides (sum of ATP + ADP) and total creatine (sum of CrP + Cr) as well as the extramitochondrial ATP/ADP- and CrP/Cr-ratios were decreased. Similar changes, significantly more pronounced, however, were found after 30 min of warm (35 degrees C) ischemia. However, if hearts were exposed to BDM during cold ischemia, extramitochondrial ATP/ADP- and CrP/Cr-ratios were increased compared to BDM-free controls. If hearts were exposed to BDM during ischemia (at 35 degrees C) and were then reperfused BDM-free, ATP/ADP- and CrP/Cr-ratios were decreased. However, if hearts were exposed to BDM during cold ischemia and were then reperfused BDM-free, extramitochondrial ATP/ADP- and CrP/Cr-ratios were unchanged. These results confirm earlier studies on the tissue protective action of BDM but point to the importance of low temperature exposure to BDM for its beneficial effect.

Actomyosin↗

PubMedDate not supplied

Influence of mitochondrial creatine kinase on the mitochondrial/extramitochondrial distribution of high energy phosphates in muscle tissue: evidence for a leak in the creatine shuttle.

The influence of mitochondrial creatine kinase on subcellular high energy systems has been investigated using isolated rat heart mitochondria, mitoplasts and intact heart and skeletal muscle tissue. In isolated mitochondria, the creatine kinase is functionally coupled to oxidative phosphorylation at active respiratory chain, so that it catalyses the formation of creatine phosphate against its thermodynamic equilibrium. Therefore the mass action ratio is shifted from the equilibrium ratio to lower values. At inhibited respiration, it is close to the equilibrium value, irrespective of the mechanism of the inhibition. The same results were obtained for mitoplasts under conditions where the mitochondrial creatine kinase is still associated with the inner membrane. In intact tissue increasing amounts of creatine phosphate are found in the mitochondrial compartment when respiration and/or muscle work are increased. It is suggested that at high rates of oxidative phosphorylation creatine phosphate is accumulated in the intermembrane space due to the high activity of mitochondrial creatine kinase and the restricted permeability of reactants into the extramitochondrial space. A certain amount of this creatine phosphate 'leaks' into the mitochondrial matrix. This leak is confirmed in isolated rat heart mitochondria where creatine phosphate is taken up when it is generated by the mitochondrial creatine kinase reaction. At inhibited creatine kinase, external creatine phosphate is not taken up. Likewise, mitoplasts only take up creatine phosphate when creatine kinase is still associated with the inner membrane. Both findings indicate that uptake is dependent on the functional active creatine kinase coupled to oxidative phosphorylation. Creatine phosphate uptake into mitochondria is inhibited with carboxyatractyloside.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗