Human serum albumin: twenty‐three genetic variants and their population distribution

Abstract

Human serum albumin has particular genetic interest because, like haemoglobin, i t is abundant in blood, easily detected in a variety of electrophoretic systems, and subject to extensive incidental screening in clinical laboratories.Nevertheless, appreciation of the diversity and frequency of albumin variation has developed slowly.The first inherited, electrophoretically detectable variant of serum albumin was described by Knedel and, independently, by Nennstiel & , Becht in 1957, but direct electrophoretic comparison of rare, inherited variants from a few unrelated families was reported only five years ago (Weitkamp et al. 1967).Predictably, several different types were found.Since then five different rapidly migrating variants (Lie-Injo et al. 1971), ten different slowly migrating variants (Weitkamp & Buck, 1972) and probably three different dimeric variants (Weitkamp et al. 1972) have been distinguished by direct electrophoretic comparison.Many other variants have been reported (see below), some of which have been found different from some of the above by direct comparison (Arends et al. 1969; TBrnoky et d.1970; Porta et al. 1972a, b ) .In this paper we distinguish at least 23 genetically determined varieties of albumin and summarize their distribution and frequency. MATERIALS AND METHODSThe designation of each albumin variant and the source of the previously published variants used in this comparison are listed in Table 1.The variants were compared in three vertical starch-gel electrophoretic systems : acetate-EDTA at pH 5.0 ; tris-lithium-succinate-citrate at pH 6.0, and tris-EDTA-borate a t pH 6.9, approximately as described by Weitkamp, Basu e f nl.(1969) except that the tris-EDTA-borate system was run for 21 hr. RESULTSIn Fig. 1 are shown starch-gel electrophoretic comparisons in the three buffer systems of 13 new or newly described variants with 17 selected variants which on previous comparisons have been distinguishable into 15 different types (Lie-Injo et al. 1971 ; Weitkamp & Buck, 1972).The distances separating the normal and variant albumin in each heterozygote for each buffer system are listed in Table 1.Under these conditions SO/CZ is not distinguishable from B, Afghanistan is not distinguishable from Kashmir, Belbm I1 is not distinguishable from Mexico, Belbm 111 and Makiritare-2