Pulmonary Intravascular Macrophages

dothelial ceUs. \U:u]ar tone could be increased by the release of TXA. is the stable metabolite of TXA.), which is a cyclooxygenase metabolite known to cause pulmonary artery constriction. Future experiments are directed at determining the mechanisms through which IV macrophages are attracted and mobilized in the lung microvasculature and at which biologically significant agents are capable of stimulating these macrophages to release AA metabolites. REFERENCES 1 Bertram TA. Intravascular macrophages in lungs of pigs infected with Haemophilus p/europneumorUtle. ~t Pathol1986; 23:681-91 2 Warner AE, Barry BE, Brain JD. Pulmonary intravascular macrophages in sheep: morphology and function of a DOYel

nxs.

constituent of the mononuclear phagocyte system. Lab Invest 1986; 55:276-88 3 Bertram TA. Quantitative morphology of peracute pulmonary lesions in swine induced by Haemophilw pleuropneumoniae. ~t Patholl985; 21:598-609 4 Reeves McMurty IF, \belkel NF. Possible role of membrane lipids in the function of the normal and abnormal pulmonary circulation. Am Rev Respir Dis 1987; 136:196-99 5 Kouzan S, Brody AR, Nettesheim I! Eling T. Production of arachidonic acid metabolites by macrophages exposed in vitro to asbestos, carbonyl iron particles, or calcium ionophore. Am Rev Respir Dis 1985; 131:624-32

.n:

Pulmonary Intravascular Macrophages* Norman C. Staub, M.D.

awareness of the pulmonary intravascular macroO urphage as an important contributor to pulmonary

hemodynamic and lymphdynamic reactions among certain animal species has developed so rapidly that this presentation can do little more than give a brief overview It has been known for more than a decade that marked differences in pulmonary hemodynamic or lymphdynamic responsiveness exist in various animal responses to a number of edematogenic agents. 'lllble 1 compares some differences between the highly reactive sheep and the almost nonreactive dog to several stimuli. The significance of this difference is critical to the selection of a representative species in which to study problems associated with human acute lung injury andARDS. What we have found during the last two years is that all species of the mammalian order Artiodactyla (even-toed, cloven-hooved) are responsive. They exhibit marked transient pulmonary hypertension following tiny injections of foreign particulate substances (Monastral blue dye, liposomes, foreign red blood cells, endotoxin and bacteria~ whereas members of three other mammalian orders (Rodentia, Lagomorpha, Carnivora) are unresponsive .... In the *From the Cardiovascular Research Institute and Department of Physiolog)l University ofCalifurnia, San Francisco, San Francisco. Supported in part by l'ro!uam Project Grant HL25816 from the National Heart, Lung ancf Blood Institute, National Institutes of Health.

Reprint requem: Dr: Staub, Cordiovt:ucular &IIBDrch Institute, 1315-Moflitt HoapUDl, Univenity of California, Son Francisco 94143-0130

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Dog Endotoxin, 1JA.g/kg Neutral lipid infusions, .05-.15 mmoll(lcg X min) Liposomes, . 1-Sjl)moVkg Monastral blue, 10 mg/kg Foreign erythrocytes, .01-1 ml

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Artiodactyla, during stimulation by a variety of particles, large quantities of thromboxane B1 can be detected in systemic arterial blood. 3 In dissecting this process, we found that the pulmonary intravascular macrophages, described by Rybicka et al• and, more recently, by Warner and Brain5 appear to be the common denominators fur this reactivit}t Using 111ln-labeled liposomes, we found that the reactive species (sheep, goat, pig, cow) retained 50% of the radioactivity in the lung for up to 12 h; the other species (rat, rabbit, dog) did not. Using 8uorescent liposomes, we found more than 90% of those retained in the lung for 2h to be intravascular and associated with large intravascular macrophage-like cells that take a nonspecific esterase stain, characteristic of the monocyte/ macrophage cell line. By electron microscopy these cells resemble mature macrophages. \1\e have been able to wash some of these cells from the pulmonary circulation using calcium and magnesium-free solutions and have placed them in primary culture, where they grow weD, although they do not devide.e They produce and secrete lysozyme, a constitutive property of macrophages. They produce superoxide anion and hydrogen peroxide when stimulated by phorbal myristate acetate or endotoxin, thromboxane B1 when stimulated by the calcium ionophore A23187, and a cytotoxic substance when stimulated by E coli endotoxin that is blocked by antitumor necrosis &ctor-alpha antibodies. Although Kochs Postulates for cause and effect have not been completely established, we hypothesize that the pulmonary intravascular macrophages are responsible for the reactivity caused by many foreign particles and substances (including endotoxin) within the pulmonary circulation. We do not know whether all species have macrophages or whether those that have them are responsive to foreign particles. Nevertheless, several unexplained pulmonary vascular reactions in sheep that have been noted by numerous investigators over the last 20 years may have a common solution, namely: reactivity of the resident population of pulmonary intravascular macrophages. REFERENCES 1 Miyamoto K, Schultz E and NC Staub. Pulmonary vascular response and lung uptake of liposomes in 7 animal species. Physiol1986; 29:177 2 Miyamoto K, Schultz E, Mitchell M and NC Staub. Systemic arterial thromhoxane concentrations after liposome infusions in three species with pulmonary intracapillary macrophages. Fed

Proc 1987; 46:1109 3 Miyamoto K, Schultz E, Heath 'I: Mitchell M, Albertine KH, Staub NC. Pulmonary intravascular macrophages and hemodynamic effects ofliposomes in sheep. J Appl Physiol (in press) 4 Rybicka K, Daly B, Migliore J, Norman JC. Intravascular

macrophages in normal calf lung. An electron microscopic study. Am J Anat 1974; 139:353-368 5 Warner AE, Brain JD. Intravascular pulmonary macrophages: novel cell removes particles from blood. Am J Physiol 1986;

250:728-32 6 Staub NC, Schultz E, Milligan S, Wang Y, Enzan K, Clarkson S, et al. Isolation, ~primary culture and properties of pulmonary intracapillary macrophages from goats and sheep. Fed Proc 1987; 46:329

capillary Recruitment in the Pulmonary Microcirculation* Wiltz W Wagner, Jr., Ph.D.

,lt the first Aspen Lung Conference on the pulmonary

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circulation in 1962, a hotly debated topic concerned which pulmonary vessels constrict during airway hypoxia. 1 Those favoring a precapillary site argued that it was only the arteries which had sufficient smooth muscle in their walls to constrict, that it was the arterial muscle which hypertrophied at high altitude, and, finally, that the precapillary site was the most suitable location fur regulating ventilation/ perfusion balance, since arterial constriction would direct blood flow to better ventilated parts of the lung befOre it reached hypoxic alveoli. The venoconstriction camp contended that the veins were the only vessels that could possibly sample the oxygen levels in blood leaving underventilated alveolar regions, and therefOre the postcapillary vessels had to be the site of hypoxic vasoconstriction. Since then, a variety of evidence has made it apparent that it is arteries of 200--300 JJ.m in diameter that constrict during hypoxia~-'~ and that the arteries themselves are capable of directly sensing airway oxygen tension.'·8 Twenty-five years ago, however, these matters were far from clear. To study this issue, Giles Filley instigated work in his laboratory in Denver to make direct microscopic observations of the surface of the living lung, reasoning that if the technique could be developed, it would be easy to determine the site of hypoxic vasoconstriction. Krah)a and deAlva et al10 made progress with the development of a thoracic window that, once implanted, permitted the pneumothorax to be aspirated so that the lung moved flush against the window pane and enabled the animal to breathe spontaneously. UnfOrtunately, their observations were hampered by lung movement. With each breath the lung slid across the window pane and, to make matters worse, the field oscillated rapidly with each heartbeat. The microscope, of course, magnified the movement. These problems were not unique to the Denver group; tissue movement has plagued all microcirculationists since Malpighis time. Dr. Filley and I began working together in the early 1960s on this project and had the good fOrtune of discovering a location on the surface of the lung lying under the second rib that moved only slightly with respiration. 11 Later, a suction manifOld was added to the bottom of the window *From the Departments of Anesthesiology and Physiology/Biophysics, Indiana University Medical School, IndianaJX>lis. Reprint requests: Dr. Wagner, MS374, 635 Barnhill Drive, Indianapolis 46205

frame so that movement was reduced to 10 JJ.m or less with each breath. 1t This permitted us to make observations of the same field over many hours and thereby to use the same arterioles, capillaries, and venules as their own controls. The stage seemed set to discover the site of hypoxic vasoconstriction. Had we done sufficient preliminary theoretic work, we would have realized that the arterioles and venules on the surface of the lung rarely exceed 50JJ.m in diameter, and that in the dog, which was our experimental animal, smooth muscle is uncommon in vessels smaller than 100JJ.m. This combination made it unlikely that we would detect vasomotion. We did not reason this out ahead of time, however, with the result that despite 25 years of attacking the canine pulmonary circulation with every sort of vasoconstrictive abuse we could imagine, we have yet to see a microvessel on the surface of the lung constrict and so have made no direct contribution to our original goal of understanding which vessels constrict with hypoxia. On the other hand, we had developed the ability to observe directly the pulmonary gas exchange vessels in a still field using high magnification in an animal with normal blood gas values, cardiac output, blood pressures, and, as best we can determine, an undamaged microvasculature. This has enabled us to make a number of studies of how the pulmonary capillaries respond to changes in pressure and flow. These observations rorm the basis of this report. The majority of our observations have been made on the surface of the left lower lobe with the animal lying in the right lateral decubitus position so that observations are made downward on the uppermost surface of the lung. This position places the field in zone 2 hydrostatic conditions, where Ppa > Palv > Ppv. 13 Zone 2 is an interesting part of the pulmonary circulation, because it is where much of the gas exchange reserve lies, both in terms of capillaries that can be recruited 1• and capillary transit times that are very X

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ARTERIAL OXYGEN TENSION (TORR) FIGURE 1. Curve represents average effect of airway hypoxia on level of capillary recruitment in upper lung in series of9 consecutive dogs. Curve swings upward at the same oxygen tension that systemic arterial hypoxemia begins. (After Wagner and Latham. 14) CHEST I 93 I 3 I MARCH, 1988 I Supplement

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