Effect of alkaline cations on cyclic 3' 5'-AMP stimulated lipolysis in rat adipocytes

In Krebs-Ringer phosphate medium, cyclic AMP had little effect on production of free fatty acids by fat cells in vitro, whereas dibutyryl cyclic AMP or epinephrine stimulated the production of free fatty acids. On the other hand, although under non-physiological condition, cyclic AMP was found to stimulate the lipolysis in simple KCl-Tris medium. The stimulation level was similar to that elicited by dibutyryl cyclic AMP. Cyclic AMP also stimulated lipolysis in LiCl-Tris or RbCl-Tris medium, but not in NaCl-Tris medium. In KCl-Tris medium, addition of divalent alkaline cations (Mg2+, Ca2+ and Sr2+, at 40 mM) completely inhibited the stimulation by cyclic AMP, but not those by dibutyryl cyclic AMP and epinephrine. No cyclic AMP-induced lipolysis was observed in homogenized or freeze-thawed cells.