Table 1.

PLA₂ activity (nmol·mg protein⁻¹·min⁻¹) in membrane and cytosolic subcellular fractions from HSAEC

Cell Fraction	Substrate*	EGTA	Ca2+
Membrane	Plasmenylcholine
	16:0, [3H]18:1	3.71±0.43	4.77±0.65
	16:0, [3H]20:4	6.23±0.63	8.48±0.52
	Phosphatidylcholine
	16:0, [3H]18:1	3.16±0.29	3.63±0.35
	16:0, [3H]20:4	6.11±0.43	7.03±0.48
Cytosol	Plasmenylcholine
	16:0, [3H]18:1	0.28±0.17	0.41±0.17
	16:0, [3H]20:4	0.85±0.15	0.93±0.18
	Phosphatidylcholine
	16:0, [3H]18:1	0.27±0.16	0.33±0.12
	16:0, [3H]20:4	0.77±0.12	0.72±0.18

Values represent means ± SE for separate measurements from 4 different cell isolations. PLA₂ activity was measured in membrane and cytosolic subcellular fractions from human small airway epithelial cells (HSAEC) using plasmenylcholine or phosphatidylcholine substrates in the absence (4 mM EGTA) or presence (1 mM Ca²⁺) of calcium.

^*Substrate composition is represented as a:b, c:d where a:b and c:d represent the chain length: number of double bonds for the aliphatic groups at the sn-1 and sn-2 positions, respectively, of the corresponding phospholipid substrate molecule.