Plasma diamine oxidase activities in renal dialysis patients, a human with spontaneous copper deficiency and marginally copper deficient rats

Objectives: Intestine and kidney are generally the most concentrated sources of the copper metalloenzyme diamine oxidase (DAO). Clinically, plasma DAO activities are used to diagnose disruptions in intestinal integrity. This study determined whether DAO activities were also affected by kidney injury or copper nutritional status. Design and Methods: Plasma DAO activities were measured in renal dialysis patients without diagnosed intestinal disease (n = 75), controls (n = 23), an adult with spontaneous copper deficiency before and after copper repletions, and in rats fed either adequate or marginal copper diets (8 or 2 mg copper/kg diet) for 7 months. Results: This study found high DAO activities in renal dialysis patients and low activities during spontaneous copper deficiency. Low activities were also seen for marginally copper deficient rats. Conclusions: Tissue injury induced elevation of DAO activities is not limited to intestinal injury, and low DAO values may be useful for assessing copper nutritional status.