[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 2.90 muM/min/mg of protein. The value of Km for the release of calcium from FSR of rectus abdominis muscle is equal to 1.25-10(-5)M, of sartotius muscle -- to 2.5-10(-5)M. Therefore, sarcoplasmic reticulum of the abdominal muscle exhibits lower capacity to retain the accumulated calcium.