Investigations on the occurrence of cytidine 3',5' monophosphate (cCMP) in tissues

A specific and sensitive radioimmunoassay (RIA) for the detection of cCMP was developed. Antibodies were prepared by immunization of rabbits with succinyl cCMP conjugated to human albumin. In the RIA commercially available 3H-cCMP was used as labeled antigen. Low amounts (0.4-2.6 pmol/g w.wt.) of immunoreactive material could be detected in extracts of brain, heart, ileum, kidney, liver, lung, spleen, testis and uterus from rats, guinea-pig and frogs. The immunoassayable material in rat liver was subjected to column chromatography on AG 1-X8 anion exchange resin. The radioimmunoassayable material isolated from the liver did not cochromatograph with authentic tritiated or unlabeled cCMP. The chromatographic properties of the immunoreactive material did not change in regenerating livers - following partial hepatectomy, or after pronase treatment. However, after treatment with pronase the amount of assayable material, extracted from the rat liver, increased. It is suggested that cCMP - as such - is not present, in detectable amounts, in extracts prepared by commonly used procedures for isolation of cyclic nucleotides. The chemical nature of the cCMP immunoreactive material isolated from rat liver is at present unclear.