A semi‐automated method for 5′‐ectonucleotidase measurement in lymphocytes

Summary We describe a simple, non‐radioactive, semi‐automated method for measuring lymphocyteccto‐5′‐nucleotidase activity in isolated cell homogenates. The method which uses inosine 5′‐monophosphate (IMP) as a substrate was optimized and requires a total of 4×10 6 lymphocytes. The reference range obtained (38·7–180·0 nmol/h per mg protein; = 106·6) agrees with other isotopic methods which use 14 C‐IMP. The simplicity, sensitivity (lower limit 10, upper limit 400 nmol/h per mL) and precision (at 114 nmol/h per mL, interday 4·2%s.d., n = 20; intraday 5·8%, n = 10) makes this method suitable for routine clinical laboratory use.