Gastrointestinal luminal polyamines: cellular accumulation and enterohepatic circulation

Area of Science:

• Gastroenterology
• Molecular Biology
• Biochemistry

Background:

• Polyamines are essential for cell growth and function.
• Their distribution and transport within the gastrointestinal tract are not fully understood.

Purpose of the Study:

• To quantify polyamine concentrations and enzyme activities in different segments of the rat gut.
• To investigate the role of enterohepatic circulation in polyamine distribution.
• To characterize the in vitro transport of polyamines in intestinal cells.

Main Methods:

• Quantification of polyamine concentrations (putrescine, cadaverine, spermine, spermidine) in rat intestinal lumen.
• Measurement of polyamine synthesis enzyme activities in intestinal tissues.
• In vivo study of [14C]putrescine secretion in pancreaticobiliary secretions.
• In vitro studies of polyamine uptake in IEC-6 cells.

Main Results:

• Duodenum and jejunum showed high concentrations of putrescine (2-3 mM) and cadaverine (1-2 mM), while ileum and colon had lower levels.
• Polyamine synthesis enzyme activity was high in the ileum, cecum, and colon, but low in the duodenum and jejunum.
• Enterohepatic circulation of polyamines was supported by the jejunum and colon, but not the ileum.
• IEC-6 cells transported putrescine via a time-, temperature-, and sodium-independent mechanism with high affinity (Km = 1.26 x 10(-6) M).

Conclusions:

• A significant concentration gradient of polyamines exists along the rat intestine.
• Enterohepatic circulation, potentially involving colonic microflora synthesis, is crucial for supplying polyamines to the proximal gut.
• A specific, high-affinity transporter mediates polyamine uptake in intestinal cells.