Pneumocytes lamellar bodies

Blumcke WD, Kessler HR, Niedorf NH, Veith FJ. Ultrastructure of lamellar bodies of type II Pneumocytes after osmium-zinc impregnation. J Ultrastruct Res 1973 42 417-433. 

Adult rats were exposed to different concentrations of n-hexane and lung tissue was then examined. The direct toxic effect to pneumocytes could be demonstrated as definite regressive alterations, such as fatty generation and change of lamellar bodies of type II pneumocytes as well as increased detachment of cells. After chronic inhalation of solvents, conspicuous aggregation of lamellar discharge material of type II pneumocytes can be seen and, probably as a result of an irritated fat metabolism, there were large lysosome-like bodies with densely packed lipid material in type I pneumocytes. 

Haller T, Auktor K, Frick M et al (1999) Threshold calcium levels for lamellar body exocytosis in type II pneumocytes. Am J Physiol 277(5 Pt 1) L893-L900... 

The lamellar bodies characteristic for type II pneumocytes can be visualised using light microscopy with the Papanicolaou stain. They are identified as deep blue granules surrounded by a clear halo (Kikkawa and Yoneda 1974). Mason and Williams (1976) have shown that a lipophilic fluorescent dye, phosphine 3R, is concentrated in the lamellar bodies. Therefore, type II pneumocytes can be identified under the fluorescent microscope by their yellow inclusion bodies (Castranova et al. 1988). 

Fig. 97. Membrane vesiculation (arrow) in a type I pneumocyte (left) and lamellar bodies in a type II pneumocyte (right) of an unmedicated male rat (No. 2573, block BNh 3767). Under pentobarbital anaesthesia (30 mg/kg), the animal was perfused from the abdominal aorta with 2.5 % glutaralde-hyde in 0.1 M sodium cacodylate buffer (pH 7.4). Postfixation with 1 % osmium te-troxide in sodium cacodylate buffer. Embedded in Epon 812 and sectioned at 50 nm. Lead citrate and uranyl acetate. Plate 2515...

After internahsation into isolated rat type II pneumocytes, SP-A and Hpid were taken up via the coated-pit pathway and resided in a common compartment, positive for the early endosomal marker EEAl but negative for the lamellar body marker 3C9 (WissEL et al. 2001). SP-A then recycled rapidly to the cell surface via Rab4-associated recycHng vesicles. Internalised lipid was transported toward a Rab7-, CD63-, 3C9-positive compartment, i.e., lamellar bodies. Inhibition of calmodulin led to inhibition of uptake and transport out of the EEAl-positive endosome and thus of resecretion of both components. Inhibition of intravesicular acidification (bafilomycin Ai) led to decreased uptake of both surfactant components. It inhibited transport out of early endosomes for lipid only, not for SP-A. 

Surfactant convertase, a diisopropylfluorophos-phate (DFP)-binding and DFP inhibitable carboxyl-esterase (Gross et al. 1997) of 70 kDa (reduced), is required for conversion of heavy density (tubular myelin) to fight density (small vesicle) subtypes of surfactant. Carboxylesterase ES-2 mRNA was localised to type II pneumocytes and alveolar macrophages but not to Clara cells (Clark et al. 1997). Lamellar bodies contain both glycosylated (70 kDa)... 

To follow the retrieval of lamellar body membrane from the cell surface in rat type II pneumocytes, Schaller-Bals et al. (2000) instilled the monoclonal antibody 3C9 into rat lungs. In vivo it was endocytosed by type II cells but not by other lung cells. In type II cells that were isolated from rat lungs by elastase digestion and cultured on plastic for 24 h, Mab 3C9 first bound to the cell surface, then was found in endosomes, vesicular structures, and multivesicular bodies and, finally, clustered on the luminal face of lamellar body membranes. 

The size of the type II pneumocytes was conspicuously increased by about 30 % in Lewis rats treated with 300 mg clofibrate/kg body weight x day by in-traperitoneal injections for 7 days (Fringes and Reith 1988). Peroxisomes proliferated and there was an increase in the number of surfactant-rich lamellar bodies (Fringes et al. 1988). 

A morphometric examination of type II pneumocytes from rats medicated for 3 days with 200 mg bromhexine per kg body weight x day demonstrated that the volumetric density of their lamellar bodies had increased from 18.0 0.9% in the controls to 20.0 0.6 % in bromhexine-medicated rats (Gil and Thurnheer 1971). 

Fig. 105. Lamellar bodies in a type 11 pneumocyte from a female white rat (breeder Winkelmann, Borchen-Kirchbor-chen) which inhaled 10 mg of a powdered cobalt-nickel alloy/ m , used in the production of hard metal hy Deutsche Edel-stahlwerke in Krefeld, 4 h per day, 5 times per week from October 2-28, 1967 for a total of 19 days. Fixed on October 30, 1967 under methitural anaesthesia by intratracheal instilla-...

In the rat, amiodarone (175 mg per kg body weight X day for 3 weeks) increased the number of lamellar bodies in type II pneumocytes (Padmava-THY et al. 1993). 

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