Determination of plasma octopamine and its level in renal disease.

A radioenzymatic assay method for the estimation of octopamine levels in plasma was developed. Preparation of the enzyme, phenylethanolamine-N-methyl transferase, dilution of the plasma sample, preparation of a suitable blank, and the assay conditions were found to have a significant effect on the sensitivity of the assay. Plasma octopamine levels were measured in a population of 33 normal individuals ranging in age from 19 to 94 years. Significantly higher plasma octopamine levels were found in the age group 70-90 years. Excluding those individuals over the age of 70 years, no significant differences in plasma octopamine levels were found for males or females, the range of values was 0 to 0.68 ng per ml, with a mean value of 0.23 ng per ml (n = 25). Examination of plasma octopamine levels in patients with severe renal disease requiring hemoperfusion dialysis, revealed a significantly higher level of plasma octopamine in renal disease (1.9 ng per ml), and an increase in plasma octopamine during dialysis; the mean level post dialysis being 2.7 ng per ml.