Paucity of Albumin Variants in Man

Abstract

PLASMA albumin in mammals is a protein of molecular weight about 69,000 and consists of a single kind of polypeptide chain¹. Until recently, the only genetic variants of this protein recognized in any mammal have been the very rare cases of ‘bis-albuminaemia’ in man^2,3. However, it has recently been reported^4,5 that some breeds of horses and zebu cattle are polymorphic (as defined by Ford⁶) for electrophoretically different albumins, and these findings have prompted me to enlarge and record some data indicating that certain human populations are not similarly polymorphic. This conclusion is to be anticipated from the fact that filter-paper electrophoresis of human plasma has been carried out routinely in clinical laboratories all over the world for more than a decade with only a few cases of bis-albuminaemia being reported, even though this condition gives a conspicuously abnormal electrophoretic pattern with two well-resolved components. In this context one may note that starch-gel, which has now widely replaced filter-paper as supporting medium, is not more sensitive than filter-paper for the study of albumin in undiluted plasma, because the large quantity of albumin present distorts the electric field in the gel, leading to reduced resolution. However, as noted also by Ashton⁵, multiple albumins can be very sharply resolved in starch gels if the plasma is diluted, and the present survey is based on this technique.