[Bioassay for plasma cholecystokinin bioactivity].

Area of Science:

• Biochemistry
• Physiology
• Endocrinology

Background:

• Plasma cholecystokinin (CCK) plays a crucial role in regulating gastrointestinal functions, including digestion and satiety.
• Accurate measurement of plasma CCK is essential for understanding its physiological roles and associated disorders.
• Existing bioassays may lack the sensitivity or specificity required for reliable CCK quantification.

Purpose of the Study:

• To develop and validate a sensitive and specific bioassay for measuring plasma cholecystokinin (CCK) levels.
• To determine fasting and postprandial plasma CCK concentrations in healthy individuals.
• To characterize the response of the bioassay to potential interfering substances.

Main Methods:

• Plasma CCK extraction using SEP-PAK cartridges.
• Quantification of CCK by measuring its ability to stimulate amylase release from rat pancreatic acini.
• Validation using a specific CCK receptor antagonist (Bt2-cGMP) to confirm specificity.

Main Results:

• The bioassay demonstrated high sensitivity, detecting CCK levels as low as 0.86 pmol/L (CCK-8 equivalent).
• Physiological concentrations of gastrin did not interfere with the assay.
• Amylase release was specifically mediated by CCK, as confirmed by the CCK receptor antagonist.
• Fasting plasma CCK levels were 0.95 ± 0.22 pmol/L, increasing to 2.98 ± 0.67 pmol/L 15 minutes postprandially.

Conclusions:

• A novel, sensitive, and specific bioassay for plasma CCK measurement has been established.
• The bioassay provides reliable quantification of CCK, distinguishing it from other gastrointestinal peptides.
• Postprandial elevation of plasma CCK confirms its role in meal response and digestion.