Organophosphates of urine, including adenosine 3′,5′-monophosphate and guanosine 3′,5′-monophosphate

Abstract

The presence of organic phosphorus compounds in the urine of healthy rats has been investigated. The animals were administered [ 32P]phosphate intraperitoneally to facilitate recognition and study of the metabolically derived P-containing components. Some of the phosphorus compounds were found to be extracted into ether at pH 4, and were not studied in detail. Systematic investigation was confined to compounds in the aqueous phase that are adsorbed by Norit A, which has high affinity for compounds with conjugated double bonds. Compounds found in this fraction were the cyclic nucleotides adenosine 3′,5′-monophosphate (3′,5′-AMP) and guanosine 3′,5′-monophosphate (3′,5′-GMP), and three unidentified compounds recognized only by rather low 32P contents. Excretion rates of the 3′,5′-AMP and 3′,5′-GMP were about 18 and 4 μg per day per 100 g rat body weight, respectively. These rates were not affected by treatment of rats with terramycin and sulphasuxidine. The cyclic 3′,5′-monophosphates of cytidine and uridine and the 5′-monophosphates of adenosine, cytidine, guanosine and uridine were either absent in the urine or present at levels too low for detection. Attention was drawn to the fact that the currently characterized organophosphorus compounds of normal urine are all phosphodiesters bearing only one negative charge per molecule. Possible implications concerning the permeability of cell walls were discussed. The specific 32P activity of the 3′,5′-GMP of 24 h rat urine samples was only about 30 % as high as that of the 3′,5′-AMP. Comparison of this value with the results of prior kinetic data on labeling of the innermost P groups of GTP and ATP of rat liver suggested that the 3′,5′-GMP is synthesized metabolically from GTP by a cyclase reaction analogous to the reaction used by synthesis of 3′,5′-AMP from ATP in liver cells of dogs. The isotope dilution method was applied to analysis of normal human urine. It was found that in man 3′,5′-GMP is excreted at a rate of approx. 1 μmole per day.