[Interaction of vanadate with the contractile system of striated muscles in the presence of natural analogs of ATP and ADP].

Vanadate produced dissociation of rigor-activated (calcium-free) fibres or rabbit m. psoas muscle in the presence of the studied various natural analogs of ATP (NTP) at optimal concentrations. By the degree of sensitivity to vanadate it is possible to establish the order ATP approximately greater than CTP greater than UTP greater than ITP greater than GTP. This series corresponds to the order for actomyosin NTPases qualitatively. Addition of corresponding NDP to fibres produced a decrease of the rigor fibres tension. Vanadate in comparable concentrations does not change the mechanical properties of fibres in the presence of NDP. At high concentration (greater than 10 mM) vanadate produced relaxation of the rigor fibres even in the absence of nucleotides. This effect is irreversible.