Gamma aminobutyric acid (GABA) and hepatic bile flow in the adult rat.
Hepatic bile canalicular membranes undergo active rhythmic contractions that may be important in the movement of bile through the hepatic biliary system (Science 212: 1041-1042, 1981). The agent(s) responsible for mediating these contractions is not known. We documented the in vivo effect of gamma aminobutyric acid (GABA), a potent amino acid neurotransmitter, on hepatic bile flow in two groups of adult male rats. One group (six animals) received 0.5 mumoles/kg/min and the other 50.0 mumoles/kg/min of a GABA-3H-GABA intravenous mixture. Serum and bile concentrations of GABA, 3H-GABA and 3H-metabolites of GABA were determined during the course of each GABA infusion period. Rats infused under identical experimental conditions with either L-alanine or saline served as controls. Serum GABA levels reached 30 and 250 times pre-infusion concentrations during the GABA infusion periods. Hepatic bile flow and electrolytes, however, remained unaltered. Alanine also had no effect on hepatic bile flow. Intact 3H-GABA and 3H-metabolites of GABA appeared promptly in bile with maximum excretion rates occurring during the 0-15 min and 30-45 min bile collection periods respectively. These results indicate that, in addition to GABA uptake and metabolism, the liver is also involved in the excretion of GABA into bile. The results do not, however, support the hypothesis that GABA is the neurotransmitter agent responsible for mediating bile canalicular membrane contractions in the adult rat hepatocyte.
D000818:Animals; D001646:Bile / Q000502:physiology*; D001648:Bile Canaliculi / Q000187:drug effects* / Q000502:physiology; D001653:Bile Ducts, Intrahepatic / Q000187:drug effects*; D008297:Male; D051381:Rats; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
D005680:gamma-Aminobutyric Acid