Distribution of metaraminol and its relation to norepinephrine

A modified fluorometric procedure of high specificity and sensitivity id described for the analysis of metaraminol (MET) in biological material. With this method the distribution of MET was studied in the rat. Except for brain, peripherally administered MET was well distributed. Organs with a large population of norepinephrine (NE) storage vesicles such as the heart, spleen and adrenal, took up relatively large amounts of MET and retained it longer than those tissues with few vesicles such as the liver, lung and kidney. MET had a longer blood half-life than described for NE in other species. In part, this can be attributed to the lack of metabolism of MET as well as our finding that MET, unlike NE, was concentrated in the cellular fraction of blood. Under the conditions of these experiments there was no close correlation on a concentration or time basis with respect to the appearance and disappearance of MET and NE in various organs. This was particularly evident in the adrenal gland where MET resembled reserpine in that one unit of drug displaced many units of catecholamines. In this case, however, we did not rule out a possible contributing effect via the CNS.