High levels of inosine monophosphate in the erythrocytes of elasmobranchs.

The acid soluble organic phosphates of the erythrocytes of three species of elasmobranchs were assayed by chromatography on Dowex 1 anion exchange columns. Organic phosphates in the peaks eluted from these columns were identified by their ultraviolet absorption spectra and by further chromatography on paper. All three species are unusual amongst the vertebrates in that their erythrocytes contain high levels of inosine monophosphate (IMP). IMP has little effect on the oxygen affinity of the hemoglobins of the two species tested.