Table 3.

Affinity of DBP from different species for the major vitamin D metabolites^*.

Species	25OHD	1,25(OH)2D	Comments
Human	5 × 108 M−1	1.5 × 107 M−1	Variation between 3 and 10 × 108, depending on buffer and DBP/genotype
Monkeys	5 × 108 M−1	1.5 × 107 M−1**	Measured in old and new world monkeys. In Cebus albicans, DBP migrates with albumin mobility but has a similar Ka
Rat	6 × 108 M−1	1.4 × 108	Measured in three strains
Rabbit	1.5 × 109 M−1	NM
Chick	4 × 108 M−1	1.7 × 107 M−1
Reptiles	NM	NM
Amphibia	2–14 × 1010 M−1	2.6 × 108M−1	Measured in 5 species

^*Measured in diluted serum at pH 7.4 and 4°C, unless specified otherwise; all values are expressed as Ka at M⁻¹ values.

^**The Ka for 1,25(OH)₂D varied between 1.2 and 2.6 × 10⁷, depending on buffer and DBP/GC genotype.

NM, not measured.