The Nature and Importance of Surface Films on Chylomicrons.

Abstract

It is generally recognized that blood transports free fat as an emulsion of minute droplets. 1 , 2 Gage and Fish 1 in their classical study of the digestion, absorption and assimilation of fat, call these droplets chylomicrons, because they enter the blood with the chyle, the milky fluid containing absorbed food from the intestine which pours directly into the blood stream.

Blood serum containing chylomicrons forms an oil-in-water emulsion system 3 which may be called the chylomicron emulsion. Oil-in-water emulsions which may be as concentrated as the chylomicron emulsion always involve a third substance, the protective or emulsifying agent which is adsorbed in the oil-water interface. Protective films are thus formed around the disperse oil drops which prevent their coalescence, thus stabilizing the emulsion. 4 The authors are the first to study the protective films on the chylomicrons and to point out their importance in the transport of fat by the blood and their presumptive importance in its assimilation from the blood and its storage and final utilization.

The experiments have all been done with chylomicrons in human serum, but the extension of the results to human plasma and to the serum and plasma of animals should be a relatively simple matter.

Consideration of the known facts with regard to protective film formation and the composition of human serum indicates that the chylomicrons should be surrounded by protein films, very possibly consisting of serum albumin, serum globulin, or both. If they are surrounded by protein films their surface properties should be those of protein. Thus their isoelectric point should fall within the range characteristic of proteins, 5 very possibly within the range of pH 4.7—pH 5.4 characteristic of the ordinary serum proteins.

The pH of the isoelectric point of the chylomicrons in human serum has been determined both by maximum flocculation and cataphoretic methods.