Intestinal surfactant-like material. A novel secretory product of the rat enterocyte.

Abstract

Surface-active phospholipid-containing particles are traditionally considered to be the product of type II pneumocytes. We now demonstrate membrane-bound lamellar cytoplasmic organelles in adult and suckling rat enterocytes that are densely reactive with phospholipid-staining reagents. These structures were seen in the basolateral space, within the intercellular junctions, and unraveling on the lumenal surface, and were more abundant after fat feeding. Light scrapings of intestinal mucosa and lumenal washings that contained these bodies, as evidenced by morphology and biochemical analysis, lowered surface tension in a pulsating bubble assay. Production by normal enterocytes of material with surfactant-like appearance and properties demonstrates that these structures are present in extrapulmonary epithelia, and extends the possible range of their function beyond gaseous exchange, e.g., solute exchange or lubrication on membrane surfaces.

A possible role for rat intestinal surfactant-like particles in transepithelial triacylglycerol transport.

“…The location of the SLP within the microvillous area is the result of routine, not necessarily optimal, cutting incidences, as these studies were intended to demonstrate intracellular particle. These particles arise from the enterocyte, not the goblet cell (5). In the absence of Pluronic L-8 1, the particles are not associated with the large cytoplasmic lipid droplets (Fig.…”

“…These structures show some morphologic resemblance to a particle we have isolated from the enterocyte apical surface. This particle is enriched for intestinal alkaline phosphatase and has a chemical, physical, and morphological resemblance to pulmonary surfactant (5,6). In addition, the particles are much more abundant after fat feeding (7) and have been found to contain relatively large amounts of IAP.…”

Rat enterocytes secrete SLPs containing alkaline phosphatase and cubilin in response to corn oil feeding

“…The small intestine is presumed to play a role in intracellular transport of absorbed triacylglycerol based on studies in rats. The SLP was observed to surround the fat droplet during fat absorption and move through the cell before entering the paracellular space by an exocytic process (7,20). Hence, our current hypothesis is that proteins involved in intracellular movement of the lipid droplet might be present in intracellular SLP.…”

“…The process of fat absorption is accompanied by the localization of an intestinal alkaline phosphatase (IAP)-containing membrane surrounding the fat droplets intracellulary (20) as well as the basolateral secretion of an IAP-containing linear membrane (presumably the same or related to the intracellular membrane) (12). We have called this membrane surfactant-like particle (SLP), because it shares features with pulmonary surfactant (7). Partly by analogy with pulmonary surfactant, we have proposed that SLP arises intracellularly rather than being endocytosed from the apical brush-border membrane (13).…”

Role of intestinal surfactant-like particles as a potential reservoir of uropathogenic Escherichia coli

“…This`surfactant-like particle' (SLP) is secreted from enterocytes and colonocytes, lowers surface tension at an air^water interface, and contains small amounts of surfactant proteins B and D [21,22] and larger amounts of surfactant protein A, particularly in the colon [23]. The turnover of the SLP associated with the apical membrane of the cell is slow [24], and its function at that site has not been explained.…”