ELMCs have high γ-glutamyl transpeptidase activity. γ-glutamyl transpeptidase (γ-GT) activity is significantly higher in ELMCs than HUVECs or freshly isolated monocytes (^*P < .05). However, ELMCs do not have increased alkaline phosphatase (ALP) activity compared with freshly isolated monocytes or HUVECs. γ-GT (A) and ALP (B) activity of freshly isolated monocytes, ELMCs, HUVECs, and MBECs were compared (n = 3). Results are expressed as enzyme activity per microgram of protein. These experiments were performed 4 times with similar results.