Influence of nucleotides, cations and nucleoside triphosphatase inhibitors on the release of ribonucleic acid from isolated rat liver nuclei

The reasons underlying reported discrepancies in the effects of ATP, ADP, adenosine 5′-[beta gamma-methylene]triphosphate, AMP + PPi, P-chloromercuribenzoate and F- on RNA efflux from isolated rat liver nuclei and on nuclear envelope nucleoside triphosphatase activity were investigated. The stimulatory effect of ADP was attributed to myokinase activity associated with the nuclei; this activity was eluted on repeated washing with nuclear incubation medium. In the absence of Ca2+ and Mn2+, ATP, adenosine 5′[beta gamma-methylene]triphosphate and AMP +PPi were found to promote release of both DNA and RNA. In the presence of 0.5 mM-Ca2+ and 9.3 mM-Mn2+, only ATP promoted RNA efflux to a significant extent. In the absence of spermidine, Ca2+ and Mn2+, nuclei released large quantities of DNA and RNA into the medium; this effect was promoted by p-chloromereuribenzoate. In the presence of the three cations, however, p-chloromercuribenzoate inhibited RNA efflux. F- caused a slight leakage of DNA from nuclei. The results are discussed in terms of models for the effects of ATP and analogues on RNA efflux and nuclear stability.