Submit a Letter to the Editor for:
P. Daniel Lew, Thomas P. Stossel
J Clin Invest. 1981;
67(1):1
doi:10.1172/JCI110000
Abstract |
Full text
|
PDF
P
hagocytic vesicles from rabbit lung macrophages produced superoxide in the presence of NADH or NADPH. At 37°C, these vesicles generated 51±7.8 nmol O2−/min per mg protein in the presence of 0.5 mM NADPH. The apparent Km for NADPH and NADH (66 and 266 μM, respectively), the pH optimum for the reaction (6.9), and the cyanide insensitivity were similar to properties of plasma membrane-rich fractions of stimulated polymorphonuclear leukocytes studied by others. The activity of the phagocytic vesicles was trypsin sensitive. The specific superoxide-generating activity of macrophage phagocytic vesicles isolated from cells incubated up to 90 min with phagocytic particles remained constant.Calcium in micromolar concentrations inhibited the NADPH-dependent O2−-generating activity of phagocytic vesicles. In a physiological ionic medium (100 mM KCl, 2.5 mM MgCl2, 30 mM imidazole-HCl, pH 6.9), a maximal inhibition of O2− generation by phagocytic vesicles of 80% was observed at 40 μM free Ca2+. The half maximum inhibitory effect was at 0.7 μM Ca2+. Variations of the calcium concentration resulted in rapid and reversible alterations in O2−-forming activity. Preincubation of phagocytic vesicles in the presence of EGTA rendered their O2− generation rate in the presence of NADPH insensitive to alterations in the free calcium concentration. This desensitization by low EGTA concentrations (≤100 μM) was reversible by the addition of excess calcium, but desensitization by high EGTA concentrations (>1 mM) was not reversible by the addition of calcium either in the presence or absence of purified rabbit lung macrophage or bovine brain calmodulins. Furthermore, trifluoperazine, a drug that inhibits calmodulin-stimulated reactions, did not alter the activity or the calcium sensitivity of the superoxide-generating system of sensitive phagocytic vesicles.Peripheral plasma membrane vesicles (podosomes) prepared by gentle sonication of macrophages possessed on O2−-generating system with similar properties to those of phagocytic vesicles.We conclude that the activated O2−-generating system of rabbit lung macrophages has its initial localization in the plasmalemma and undergoes subsequent internalization into phagocytic vesicles, where it can function for prolonged periods of time. Calcium at concentrations likely to exist in macrophage cytoplasm exerts a regulatory effect on the activated system.
Guidelines:
The Editorial Board will only consider letters that we deem relevant and of interest to our readers. We will not post data that have not been subjected to peer review, nor will we post letters that are essentially a reiteration of another letter. All accepted letters will be posted on our website within one week of acceptance. The Editors reserve the right to edit any letter for length, content, and clarity. Authors of all accepted letters will be asked to preview any changes. Authors will be notified by e-mail if their letters were not accepted. As this is a final decision, no appeals will be considered.
Specific requirements: All letters must be 400 words or fewer. You may enter the letter as plain text or HTML, if you wish. The author's name and e-mail address are required, and will be posted with the letter. All possible conflicts of interest must be noted, even if they are not posted. If you wish to include a figure (keep in mind that non-peer-reviewed data will not be posted), please contact the editor directly at editors@the-jci.org.
