FroZen Cells validated for cAMP testing: Apelin, APJ. Human Recombinant, in CHO-K1 host cell. We provide one vial of frozen cells (2.5 million cells/vial). Some of our Frozen cells may be restricted for sale in specified countries. Please inquire at your local sales office for more information. You are authorized to utilize these frozen cell preparations one time only. Any attempt to transfer, re-use, or propagate these cells is expressly unauthorized and a violation of the product terms and conditions of sale.