Surfactant protein A is localized at the corners of the pulmonary tubular myelin lattice |
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Authors: | W F Voorhout T Veenendaal H P Haagsman A J Verkleij L M van Golde H J Geuze |
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Institution: | Department of Cell Biology, Medical School, University of Utrecht, The Netherlands. |
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Abstract: | Immunogold labeling on sections of a freeze-substituted tubular myelin-enriched fraction isolated from a bronchoalveolar lavage of rat lung showed that surfactant protein A (SP-A) occurs predominantly at the corners of the tubular myelin lattice. Seventy-nine percent of the gold particles were located within 20 nm from a corner. Extracellular SP-A was detected only in the tubular myelin lattice and not in vesicles or secreted lamellar bodies. Ultra-thin cryosections of rat lung fixed in vivo showed that intracellular SP-A was distributed homogeneously over the stacked membranes of lamellar bodies in alveolar Type II cells. The presence of SP-A at the corners of the tubular myelin lattice suggests an important role of this protein in the formation and/or maintenance of this highly ordered lattice. |
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