Cyclin nucleotide binding sites of the smooth endoplasmic reticulum from normal and neoplastic liver in the rat

The studies are presented which demonstrate that smooth endoplasmic membrane of normal liver has a single apparent binding site for cAMP with a KD of 0.6 X 10(-8) M. In contrast to this, however, cyclic AMP binding to the intracellular membrane of hepatoma 7800 exhibit two binding sites; the binding constant of one site on the tumor membrane is comparable to that of the normal liver whereas the value of the second intrinsic association constant differ by a factor of 10. It is suggested that there may be an association between abnormal cyclic nucleotide metabolism and the intracellular membrane modulation of the expression of genetic information in normal and neoplastic cells.