[Effect of fatty acids on Ca2+-channels in sarcoplasmic reticulum in skeletal muscles].

It has been shown that the unsaturated free fatty acids evoke calcium release from sarcoplasmic reticulum vesicles of the rabbit skeletal muscle by means of the increase of permeability of terminal cisternae Ca-release channel. The effect of free acids was the same as the effects of Ca-channel activators, caffeine and silver ions, and was blocked by ruthenium red and procaine. Saturated fatty acids did not stimulate the release of Ca from reticulum.

[Catalytic and transport cycle of sarcoplasmic reticulum Ca(2+)-ATPase].

Recent information on mechanisms of ATP hydrolysis and relevant transport of calcium ions by the membrane-bound Ca(2+)-ATP-ase of the sarcoplasmic reticulum is summarized. Stages of the catalytic and transport cycles of the Ca(2+)-ATP-ase and conformational states of the enzyme are considered in detail.

[The effect of verdazyl radicals on Ca2+ metabolism in preparations of heavy sarcoplasmic reticulum].

Three verdazyl radicals were studied for their effect on calcium accumulation and outflux (passive and Ca- or caffeine-induced) and conformational state of the Ca-ATPase. All three compounds differently affected the ATP-dependent Ca-accumulation. Their effect on the Ca-release from the sarcoplasmic reticulum vesicles could not be explained by their influence on the Ca-accumulation system.

[Effect of caffeine and glycerin on the Ca transport system of sarcoplasmic reticulum fragments from frog skeletal muscles].

Parameters of the Ca2+-ion transport system by a fragmented sarcoplasmic reticulum isolated from phasic and tonic frog skeletal muscles were investigated under the action of caffeine or caffeine in combination with glycerol. No changes were observed in the Ca-transport system of a light fraction of the sarcoplasmic reticulum under the influence of caffeine and caffeine-glycerol combination. Caffeine reduced the value of Ca/ATP and enhanced the outflux of Ca2+-ions from membrane fragments of the caffeine-sensitive sarcoplasmic reticulum fraction of both the muscles; the combined effect of caffeine and glycerol was analogous to the action of caffeine applied alone.

[Passive binding of Ca2+ by fragments of the sarcoplasmic reticulum of frog skeletal muscles].

A calcium binding characteristics of outside and inside vesicles as well as effects of K+, Mg2+, and acetylcholine cation on the calcium binding were studied in fragments of sarcoplasmic reticulum (SRF), isolated from frog femoral and abdominal muscles; high permeability of the preparations for Ca2+ was produced by incubation with I mM EDTA (pH 8-8.5) or with 5-10 microM ionophor X587A. Three types of Ca2+ binding were observed in the both SRF preparations: two of them exhibited the specific binding with high (K1) and low (K2) affinity and one type of unspecific binding with low affinity (Kunsp).

[Causative factor of Ca2+ transport reduction by sarcoplasmic reticulum fragments under the action of acetylcholine].

The uncoupling of Ca2+ uptake and ATP hydrolysis by acetylcholine (ACh) and choline has been demonstrated on fragmented sarcoplasmic reticulum (FSR) isolated from femoral muscles of Rana ridibunda. The uncoupling depends on the content of oxalate in the incubation medium. An increase in the Ca/ATP ratio caused by serum albumin observed at low oxalate concentrations is indicative of participation of free fatty acids in the uncoupling effect of ACh and choline.

[Functional properties of fragments of the sarcoplasmic reticulum of the fast and slow muscles of Rana ridibunda frogs].

It has been demonstrated that fragmented sarcoplasmic reticulum (FSR) from slow rectus abdominis muscle exhibits lower Ca/ATP ratio, lower Ca2+ uptake and higher Ca2+ release from the vesicles as compared to the reticulum from fast sartorius muscle. The rate of Ca2+ uptake by sartorius muscle is equal to 4.78, that by rectus abdominis muscle -- to 2.

[Effect of acetycholine on the Ca2+ transport system in sarcoplasmic reticulum of frog skeletal muscle].

In fragments of sarcoplasmic reticulum of the frog abdominal straight muscle the functional properties of Ca2+ transport and effect of acetycholine on those properties were studied. The rate of Ca2+ accumulation was decreased due to stimulation by acetylcholine the Ca2+ out-flow from the reticular vesicles. The ratio Ca2+/ATP decreased and the Ca2+-ATPase activity was increased.