MEASUREMENT OF PHOSPHOINOSITIDE-SPECIFIC PHOSPHOLIPASE-C ACTIVITY IN MONONUCLEAR LEUKOCYTES FROM ATOPIC AND NORMAL SUBJECTS

The intracellular inositol pathway is an important route for cell activation and relies on the stimulation of membrane-bound phosphoinositide-specific phospholipase C (PLC). Previously we have shown abnormalities of inositol metabolism in mononuclear cells (MNL) in atopic dermatitis (AD) using an indirect method. We now describe a direct method of measuring PLC activity in membrane and cytosol preparations of MNL in AD. We compare PLC activity in AD with that in normal controls and examine the effect of substrate concentration and nucleotide stimulation on the system. Our findings show increased membrane-bound PLC activity in AD compared with normal controls. Non-specific stimulation of AD PLC activity by nucleotides suggests that the enzyme of atopics is more sensitive to substrate-driven activity than that of non-atopics.