Subcellular localization of angiotensin-converting enzyme in the human alveolar macrophage

The present investigation was performed in order to elucidate the subcellular localization of angiotensin-converting enzyme (ACE) in human alveolar macrophages. A pure population of alveolar macrophages was obtained by centrifugal elutriation of bronchoalveolar lavage (BAL) fluid from seven sarcoid patients. The cells were homogenized by sonication and the postnuclear supernatant was fractionated on a discontinuous sucrose gradient. Fractions of particulate material were collected and characterized by marker enzymes. The distribution pattern of ACE closely resembled that of NADPH-cytochrome-c-reductase and sialyltransferase, markers of the endoplasmic reticulum and the Golgi complex, respectively, indicating a common localization. This localization is compatible with synthesis taking place in the alveolar macrophage.