Determination of nonspecific lipid transfer protein in rat tissues and Morris hepatomas by enzyme immunoassay.
Rat tissues contain a nonspecific transfer protein which in vitro mediates the transfer of diacylphospholipids as well as cholesterol between membranes. This protein appears identical to sterol carrier protein. A specific enzyme immunoassay for this protein was developed using antibodies raised in rabbits, against a homogeneous protein from rat liver. This assay was based on the very high affinity of the nonspecific lipid transfer protein for polyvinyl surfaces. A reproducible adsorption was achieved by presenting the protein to the surface in the presence of a large excess of bovine serum albumin. The adsorbed protein was detected with specific immunoglobulin (IgG) isolated by antigen-linked affinity chromatography and a goat anti-rabbit IgG-enzyme conjugate. Adsorption was proportional to the amount of protein present, giving rise to a linear standard curve. The enzyme immunoassay measured transfer protein levels in the range 0.2-2 ng. The highest concentrations of transfer protein were found in liver and intestinal mucosa. Levels in other tissues including brain, lung, kidney, spleen, heart, adrenals, ovary and testis were 5-10-fold lower than in liver. In the fast-growing Morris hepatoma 7777 the concentration of nonspecific lipid transfer protein was approximately one-tenth of that measured in the host liver, whereas a reduction of 65% was observed in the slow-growing Morris hepatomas 7787 and 9633. Subcellular distribution studies showed that approx. 70% of the transfer protein was present in the soluble supernatant fraction.
D000818:Animals; D002352:Carrier Proteins / Q000032:analysis*; D007124:Immunoenzyme Techniques; D008099:Liver / Q000032:analysis; D008114:Liver Neoplasms, Experimental / Q000032:analysis*; D008722:Methods; D010714:Phosphatidylethanolamines / Q000378:metabolism; D011817:Rabbits; D051381:Rats; D011915:Rats, Inbred BUF; D013347:Subcellular Fractions / Q000032:analysis; D014018:Tissue Distribution
D002352:Carrier Proteins; D010714:Phosphatidylethanolamines; C030363:lipid transfer protein