Barbiturate-induced choleresis: possible independence from microsomal enzyme induction

Area of Science:

• Pharmacology
• Hepatology
• Biochemistry

Background:

• Barbiturates are known to affect liver function.
• Hepatic microsomal systems, including cytochrome P-450, play a crucial role in drug metabolism.
• Bile secretion is vital for digestion and detoxification.

Purpose of the Study:

• To investigate the effects of four barbiturates on bile secretion.
• To examine the impact of these barbiturates on the hepatic microsomal system.
• To determine the relationship between barbiturate-induced changes in bile flow and liver enzyme activity.

Main Methods:

• Anesthetized rats were administered four barbiturates (phenobarbital, barbital, thiopental, pentobarbital) intraperitoneally for four days.
• Liver weight, cytochrome P-450 concentration, and pentobarbital sleeping time were measured.
• Electron microscopy was used to assess hepatocyte ultrastructure.
• Bile flow was measured and analyzed for bile acid independent flow.

Main Results:

• Phenobarbital, barbital, and thiopental increased liver weight, cytochrome P-450 concentration, and induced smooth endoplasmic reticulum hypertrophy.
• All four barbiturates, including pentobarbital, significantly increased bile flow, primarily through the bile acid independent pathway.
• No correlation was found between increased bile flow and elevated cytochrome P-450 levels.

Conclusions:

• Barbiturate treatment in rats leads to increased bile flow.
• This increase in bile flow appears to be independent of hepatic microsomal enzyme induction caused by these drugs.
• Pentobarbital, while not inducing liver enzymes, still enhances bile secretion.