[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).

[Some properties of transport ATPases in functionally different muscles].

The properties of Ca-transporting system in sarcoplasmic reticulum membranes in fast and slow frog muscles as well as some properties of sarcolemma Na, K-ATPase of the same object were investigated. The rate of Ca2+ uptake, Ca-ATPase activity and Ca/ATP ratio for the reticulum of fast muscle demonstrated higher values than those for the reticulum of slow muscle. The rate of Ca2+ accumulation by the fragments of the rectus reticulum and Ca/ATP ratio were found to decrease under the influence of acetylcholine (0.

[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.