[Modification of the functional properties of sarcoplasmic reticulum Ca-ATPase in hypercholesterolemia]. / Modifikatsiia funktsional'nykh svoistv Ca-ATFazy sarkoplazmaticheskogo retikuluma pri giperkholesterinemii.

Using alamethicin, permitting the measurement of genuine catalytic enzyme activity, hypercholesterolemia was shown to cause a 10-30% reduction of specific Ca-ATPase activity registered at 37 degrees C and the shift of Arrhenius plot in 20-30 degrees C temperature range. Reconstruction of delipidated Ca-ATPase of sarcoplasmic reticulum membranes by egg lecithin in animals with hypercholesterolemia does not lead to the recovery of Arrhenius plot. The data obtained demonstrate that modification of temperature-dependent Ca-ATPase activity in hypercholesterolemia is associated with the changes in the polypeptide with a catalytic function and is not induced by the changes in phospholipid enzyme surroundings.

[Protective effect of alpha-tocopherol on the Ca2+-transport system of the sarcoplasmic reticulum membranes in hypercholesterolemia]. / Zashchitnoe vliianie al'fa-tokoferola na Ca2+-transportiruiushchuiu sistemu membran sarkoplazmaticheskogo retikuluma pri giperkholesterinemii.

The effect of antioxidant--alpha-tocopherol--on Ca2+-transporting system in sarcoplasmic reticulum (SR) of the rabbit skeletal muscles was studied in hypercholesterolemia (HC). alpha-tocopherol administration to animals with HC produced a break on the curve of temperature dependence of Ca-ATPase activity at about 20 degrees C, that disappeared in HC, increased the rate of "rapid" SH-group binding by thiol reagents, and normalized the level of unsaturated fatty acids in SR membranes without altering phospholipid content. It is suggested that the damage of Ca-ATPase in HC is mainly due to activation of lipid peroxidation.

[Lipid peroxidation and the functioning of the Ca pump of the sarcoplasmic reticulum of skeletal muscle in hypercholesterolemia]. / Perekisnoe okislenie lipidov i funktsionirovanie Ca-nasosa sarkoplazmaticheskogo retikuluma skeletnykh myshts pri giperkholesterinemii.

During prolonged hypercholesterolemia (HCh), there was a reduction in the efficacy of Ca-pump function of the sarcoplasmic reticulum (SR) of rabbit skeletal muscles, an increase in cholesterol content, and intensification of lipid peroxidation in SR membranes. Supplementation of the cholesterol-rich diet with alpha-tocopherol effectively prevented dysfunction of the SR Ca-pump and reduced the enhanced LPO level in SR membranes without having any effect on cholesterol content in blood serum and SR membranes. The increase in the LPO level seems likely to be primarily responsible for abnormalities in the SR Ca-pump during HCh.

[Effect of cholesterol on the cooperativeness of the Ca-ATPase of the sarcoplasmic reticulum in rabbit skeletal muscle]. / Vliianie kholesterina na kooperativnost' Ca-ATFazy sarkoplazmaticheskogo retikulma skeletnykh myshts krolika.

Cooperative properties of Ca-ATPase of the sarcoplasmic reticulum (SR) of rabbit skeletal muscles were examined in health and hypercholesterolemia. As the concentration of ATP was raised (from 50-100 microM to 5 mM) the Hill ratio (Nh) for ATP increased from 0.4 to 3.2. It is assumed that increased cooperative interaction between Ca-ATPase polymers led to a rise in the efficacy of Ca-pump work. Under the conditions described the Nh for UTP increased from 0.43 to 1.0. During hypercholesterolemia (1 g/kg cholesterol for 1, 3 and 6 months), the maximal values of the Nh for ATP did not exceed 2.0, whereas those for UTP 1.0.

[Effect of disseminated myocardial necrosis on ATPase activity, Ca2+ transport, and lipid peroxidation in cardiac mitochondrial and microsomal membranes]. / Vliianie rasseiannogo nekroza miokarda na ATF-aznuiu aktivnost', transport Ca2+ i perekisnoe okislenie lipidov membran mitokhondrii i mikrosom serdtsa.

Isoproterenol-induced (5 mg/kg) disseminated necrosis of the rabbit myocardium led to a decrease in the efficiency of calcium pump of sarcoplasmic reticulum fragments. This was shown by the reduced Ca/ATP ratio, as well as by Ca2+ and Ca2+ ATPase accumulation rate. In these conditions, calcium transport to mitochondria increased. Lipid peroxidation plays a definite role in the impairment of membrane permeability since the concentration of malonic dialdehyde rises in microsomal and mitochondrial fractions.U

[Calcium transport and ATPase activity of mitochondria and sarcoplasmic reticulum fragments of rabbit heart and muscle in hypercholesteremia]. / Transport kal'tsiia i ATF-aznaia aktivnost' mitokhondrii i fragmentov sarkoplazmaticheskogo retikuluma serdtsa i myshts krolikov pri giperkholesterinemii.

The rabbits were fed cholesterol diet (1 g/kg) for 3--7 months. As a result there was an increase in cholesterol concentration in mitochondrial membranes and fragments of sarcoplasmic reticulum (SPR) of the myocardium and skeletal muscles. Saturation of the membranes with cholesterol led to a decrease in the efficiency of SPR Ca-pump manifested by reduced Ca/ATP ratio and increased Ca2+ outflow rate from SPR. Under these conditions the rate of Ca2+ accumulation was higher in SPR than in the mitochondria. The activity of Mg2+, 2,4 DNF ATPase of the mitochondria declined in hypercholesterolemia.