Intracellular and extracellular compartments of phospholipids in the lungs of rats were examined 28 days after intratracheal injection of silica (200 mg/kg). All compartments containing phospholipids were elevated, but the largest increases were seen in the intracellular and extracellular pulmonary surfactant. Intracellular pulmonary surfactant increased 123-fold from 1.18 +/- 0.65 to 144.9 +/- 53.8 and the extracellular surfactant increased 22-fold from 1.17 +/- 0.04 to 25.1 +/- 7.1 mg per pair of rat lungs respectively. The phospholipid composition of intracellular and extracellular surfactant did not change in response to silica, except for an almost 2-fold increase in the percentage of total phosphatidylinositol in both compartments. The phospholipid content of the lungs increased from 24.9 +/- 4.6 to 268.6 +/- 20.8 mg, with the intracellular and extracellular surfactant accounting for 59.1 and 24.6% of this total increase respectively. These data demonstrate that the major increases in the phospholipid content of the lungs induced by silica is associated with the pulmonary-surfactant system.

Carcinogenic potential of the thiazolidinedione antidiabetic troglitazone was assessed in 104-week studies in mice and rats. Mice were given 50, 400, or 800 mg/kg, male rats 100, 400, or 800 mg/kg, and female rats 25, 50, or 200 mg/kg. Vehicle and placebo controls were included. Survival was significantly decreased in both sexes of both species at high doses, but was adequate for valid evaluation of carcinogenicity. Hypertrophy and hyperplasia of brown adipose tissue was observed in both species at all doses, and fatty change and hypocellularity of bone marrow was noted in mice at all doses and in female rats at 50 and 200 mg/kg. Hepatocellular vacuolation was observed in mice at 400 and 800 mg/kg, and centrilobular hepatocellular hypertrophy occurred in rats at > or = 200 mg/kg. Ventricular dilatation, myocardial fibrosis, and atrial myocyte karyomegaly in male rats at 400 and 800 mg/kg and female rats at all doses were morphologically similar to spontaneous lesions, but incidence and severity were increased compared with controls. In mice, the incidence of hemangiosarcoma was increased in females at 400 mg/kg and in both sexes at 800 mg/kg. The incidence of hepatocellular carcinoma was increased in female mice at 800 mg/kg. Troglitazone exposure [AUC((0-24))] at the lowest dose associated with increased tumor incidence in mice was 16 times human therapeutic exposure at 400 mg daily. No tumors of any type were increased in rats at exposures up to 47 times therapeutic exposure.

Pulmonary interstitial macrophages (IM) were isolated from rat lungs by an Fc gamma receptor-based affinity technique coupled with multiparameter flow cytometry. Single cell suspensions obtained by collagenase digestion of extensively perfused and lavaged lungs were applied to carpets of opsonized sheep red blood cells (SRBC-IgG) bound to plastic tissue culture flasks. At 0-4 degrees C, optimal binding of lung cells occurred within 60 min at plating densities of 1-2 X 10(6) lung cells/cm2 when the SRBC substrate was opsonized with 10 micrograms/ml anti-SRBC IgG. Nonadherent cells were removed by gently rinsing the plates and adherent cells were recovered by lysing the SRBC-IgG substrata. By light microscopy, the mixture of adherent cells was comprised of mononuclear cells (approximately 54%), many of which appeared to be macrophages, lymphocytes (approximately 20%), polymorphonuclear leukocytes (approximately 15%), plasma cells (approximately 8%), eosinophils (approximately 2%), and mast cells (approximately 0.5%). The cells which adhered to the SRBC-IgG monolayers were further resolved into subpopulations by multiparameter flow cytometry and sorted according to their electro-optical characteristics. One subpopulation appeared morphologically to be macrophages, and greater than 90% of these cells readily phagocytized SRBC-IgG in vitro. Peroxidase staining of this population was minimal, indicating that these cells were not blood monocytes (BM). Using a method by which alveolar macrophages (AM) were prelabeled with SRBC-IgG in situ, we demonstrated that alveolar macrophages constituted only approximately 5% of the total adherent cell population. We concluded from these observations that the macrophage population harvested in this manner were neither BM nor AM, but, rather, were harvested from the lung's interstitial compartment. Flow cytometric analyses indicated that the IM exhibited electro-optical characteristics intermediate between those of BM and AM, which is consistent with the concept of the lung's interstitium as a maturation compartment for the BM prior to migration into the alveolar compartment. However, the IM more closely resembled the BM than the AM, indicating that if the IM is in fact a precursor to the AM population, substantial maturation or differentiation must occur subsequent to its migration into the alveolar compartment. This isolation technique will be useful for harvesting highly purified IM for in vitro investigations.

No abstract

No abstract