Immune system and thiols: some peculiarities of thiol exchange.

We show that for the system of SH-containing compounds of the organism (cysteine, in particular) there are conditions leading to immunosuppression, which occurs when the level of amino acid cysteine in blood serum increases. The arising "overload" of free sulfhydryl groups inactivates antibodies of the IgM class of any specificity restoring disulphide intramolecular bonds and then the number of immune antibody-producing cells, mitotic activity of T- and B-lymphocytes and interleukin-2 synthesis are lowered and the mobility of surface immunoglobulin B lymphocytes receptors is damaged. Determination of total blood sulfhydryl groups for diagnostics of developing immunodeficiency disorder is not informative because of the high individual fluctuation of blood sulfhydryl groups number.

Hormone regulation of cardiac energy metabolism. I. Creatine transport across cell membranes of euthyroid and hyperthyroid rat heart.

Hyperthyroid rat heart was studied with the purpose of identifying the mechanism for the significant decrease in total creatine (free creatine plus phosphocreatine) observed in this pathology and its consequences on heart function. Administration of L-thyroxine in doses of 50-100 micrograms/100 g of body weight during a week resulted in a reversible decrease of the total creatine by 40-50%. Simultaneously, remarkable changes in the creatine transport system across the cardiac cell membranes were observed: both the maximal rate of its active uptake and its passive movement along its concentration gradient were enhanced.

[The functional coupling between MM isozyme of creatine phosphokinase (EC 2.7.3.2.) and MgATPase of myofibrils and (Na, K)ATPase of plasma membrane in heart cells].

The functional role of particulate MM isozyme of creatine phosphokinase (CPK) bound to heart myofibrils has been studied. It has been shown that in the presence of heart myofibrils and MgATP creatine phosphate can be used to rephosphorylate ADP formed in the MgATPase reaction. The rate of creatine phosphate splitting is determined by the kinetic properties of myofibrillar MgATPase and by the kinetic parameters of myofibrillar CPK.

[Functional characterization of the creatine phosphokinase reactions in heart mitochondria and myofibrils].

The kinetic properties of MM-isozyme of creatine phosphokinase (CPK) bound to heart myofibrils have been determined experimentally. It has been shown that CPK isozymes bound to the heart myofibrils and mitochondria are electrophoretically different, but have very similar kinetic properties. For both isozymes the ATP formation reaction is preferable.