Non-parallel enzyme secretion from rat pancreas: in vivo studies

Area of Science:

• Gastroenterology
• Physiology
• Biochemistry

Background:

• The pancreas secretes digestive enzymes like amylase, lipase, and chymotrypsinogen.
• Understanding the regulation of pancreatic enzyme secretion is crucial for digestive health.

Purpose of the Study:

• To investigate the differential secretion of pancreatic enzymes in rats.
• To determine if pancreatic enzyme secretion occurs from a single or multiple storage pools.
• To examine the effect of hormonal and pharmacological stimulation on enzyme secretion patterns.

Main Methods:

• Measurement of amylase, lipase, and chymotrypsinogen in pancreatic juice of anesthetized rats.
• Intravenous administration of cholecystokinin-pancreozymin and secretin.
• Administration of pilocarpine and secretin.
• Inhibition of protein synthesis using cycloheximide.
• Development of a mathematical model to interpret secretion patterns.

Main Results:

• Stimulation with cholecystokinin-pancreozymin and secretin altered enzyme proportions, decreasing amylase ratios.
• Pilocarpine and secretin also induced non-parallel enzyme secretion, but secretin alone did not.
• Cycloheximide did not prevent the changes in enzyme proportions, indicating pre-synthesized proteins are involved.
• A mathematical model suggested two distinct enzyme pools with different proportions.

Conclusions:

• Exocrine pancreatic proteins are stored in at least two pools with differing enzyme compositions.
• A small, stimulation-insensitive pool accounts for basal secretion.
• A larger, predominant pool is responsible for increased protein output upon stimulation.