A bradykinin-like substance in rat stomach

Area of Science:

• Pharmacology
• Biochemistry
• Gastroenterology

Background:

• The presence and function of endogenous peptides in the mammalian gastrointestinal tract are areas of ongoing research.
• Bradykinin (BK) and related peptides are known for their diverse physiological roles, including effects on blood pressure and smooth muscle contraction.

Purpose of the Study:

• To characterize a bradykinin (BK)-like substance (P1) isolated from rat stomach tissue.
• To identify another biologically active substance (P2) detected during the purification of P1 and elucidate its properties.

Main Methods:

• Extraction of rat stomach tissue using various solvents (acetic acid, n-butanol, water, methanol).
• Purification and characterization of peptide substances using gradient and equilibrium chromatography on SP-Sephadex C-25 columns.
• Estimation of molecular weight by gel chromatography and assessment of biological activity on isolated rat uterus and duodenum, and rabbit blood pressure.

Main Results:

• A BK-like peptide (P1) was isolated, exhibiting distinct chromatographic behavior and an apparent molecular weight over 1,300 Da, differentiating it from BK, kallidin, and methionyl-lysyl-bradykinin (MLBK).
• A second substance (P2) was identified, causing uterine and duodenal contraction, with hypotensive effects similar to serotonin (5-HT).
• P2 was confirmed to be serotonin (5-HT) based on chromatographic retention times and its pharmacological profile.

Conclusions:

• A novel mammalian BK-like peptide, distinct from known kinins, exists in the rat stomach.
• Serotonin (5-HT) is present in rat stomach extracts and possesses contractile activity on smooth muscles and hypotensive effects.