Samples were collected by injecting rats with normal saline or 7 M ethanol intraperitoneally (1 ml/100 g body weight) and quickly removing and freezing the liver 30 minutes post injection. Appropriate extracts were prepared for measurement of metabolites required to calculate a tissue free cytosolic phosphate concentration. The free cytosolic Pi is estimated from the participants of the guanine nucleoside phosphorylase reaction. Additionally, the cytosolic pH and free magnesium were also determined by measurement of bicarbonate and citrate and isocitrate. The equilibrium constant (KGNP) was corrected for intracellular pH and free magnesium as determined in both the control and ethanol-treated groups. Corrections were made for extracellular metabolite contributions as appropriate. It was assumed that all remaining guanine, guanosine and ribose-5-phosphate was available in the cytosol (not segregated or otherwise unavailable to the enzyme). The level of free cytosolic Pi calculated in the control group agreed well with the level usually """"""""seen"""""""" by NMR in the control group while ethanol administration caused an increase in the free Pi level.
