Plasma Met-Enkephalin and Leu-Enkephalin in Chronic Renal Failure

Plasma met-enkephalin and leu-enkephalin has been measured ina group of 28 patients with chronic renal failure, to discoverwhether these opioids are affected by standard haemodialysisand haemofiltration. Met-enkephalin was markedly higher (P<0.001) in uraemic patientsthan in a group of 13 normal subjects, and was directly relatedto plasma creatinine (r=0.60; P<0.01) and to plasma urea(r=0.36; P=0.06). In contrast, leuenkephalin was suppressedin uraemic patients (P<0.001). Met-enkephalin fell slightlybut significantly (P<0.02) after both haemodialysis and haemofiltration;however, on average it remained at concentrations four timeshigher than normal. No changes in plasma leu-enkephalin wereobserved after haemodialysis and haemofiltration. The cause(s)of the altered plasma concentrations of these opioid substancesremains to be clarified.