Modulation of adenylate cyclase activity by a cytosolic factor following chronic opiate exposure in neuroblastoma x glioma NG108-15 hybrid cells

A soluble cytosolic factor from neuroblastoma x glioma NG108-15 hybrid cells stimulates adenylate cyclase activity in isolated membrane preparations. This cytosolic component is heat stable, pronase insensitive, has a molecular weight less than 350 daltons and an absorbance peak at 260 nm. The stimulation is immediate, independent of Ca⁺⁺ and exhibits a sigmoidal concentration dependency curve. The cytosolic factor stimulated adenylate cyclase activity in etorphine treated cells (100 nM etorphine, 16 hrs) to a greater extent than in control cells. In addition, cytosolic factor derived from etorphine treated cells, as compared to control cells, displayed an increased capacity to stimulate adenylate cyclase. It is suggested that the observed cytosolic factor may be adenosine and that cells chronically treated with an opiate exhibit an increase in both concentration and sensitivity to this agent.