Comparative study of primates' transcortin: immunoreactivity and steroid-binding activity

Area of Science:

• Primate evolutionary biology
• Biochemistry
• Immunology

Background:

• Transcortin (corticosteroid-binding globulin, CBG) plays a crucial role in regulating corticosteroid levels.
• Understanding the evolutionary trajectory of CBG provides insights into primate adaptation and speciation.
• Previous studies have established the importance of CBG in various mammalian species.

Purpose of the Study:

• To investigate the phylogenetic distribution and evolutionary aspects of transcortin (CBG) in primates.
• To examine the immunoreactivity of primate transcortin with anti-human transcortin antibodies.
• To assess the cortisol-binding activity of transcortin across different primate groups.

Main Methods:

• Utilized radioimmunoassay techniques with 125I-labelled human transcortin and anti-human transcortin antiserum.
• Tested plasma samples from various primate groups including Catarrhini, Platyrrhini, and Prosimiae.
• Assessed cortisol-binding activity in primate plasma samples.

Main Results:

• Transcortin immunoreactivity was detected in Catarrhini (Old World monkeys and apes) but not in Platyrrhini (New World monkeys) or Prosimiae.
• Cortisol-binding activity was present in most primates, with notable exceptions in certain Platyrrhini species.
• Thyroxine-binding globulin (TBG) immunoreactivity was observed only in plasma from Pan (chimpanzee).

Conclusions:

• The presence of immunoreactive transcortin and TBG in highly evolved apes aligns with primate cladogenetic classifications.
• Evolutionary modifications in transcortin structure may have occurred without compromising its cortisol-binding function.
• Specific Platyrrhini species may have unique adaptations related to cortisol regulation due to absent or altered transcortin function.