Amino acid utilisation in isolated hepatocytes from rainbow trout

Area of Science:

• * Comparative physiology
• * Fish metabolism
• * Biochemistry

Background:

• * Trout hepatocytes' metabolic capabilities are crucial for understanding energy utilization in fish.
• * Amino acid, lactate, and palmitate metabolism are vital for fish survival under varying conditions.

Purpose of the Study:

• * To investigate the utilization of amino acids by isolated trout hepatocytes.
• * To compare amino acid utilization with that of lactate and palmitate.
• * To assess the role of amino acids in CO2 production and gluconeogenesis in trout.

Main Methods:

• * Isolated trout hepatocytes were used to measure substrate utilization.
• * Rates of CO2 production and glucose synthesis (gluconeogenesis) were quantified.
• * Enzyme activity, specifically phosphoenolpyruvate carboxykinase, was measured.

Main Results:

• * In fed fish, amino acids (alanine, serine, asparagine, glycine) and lactate were preferentially used for CO2 production over palmitate.
• * Starvation and exercise increased palmitate utilization for CO2 but decreased lactate and amino acid utilization.
• * Amino acids, particularly serine and asparagine, contributed to gluconeogenesis, with rates increasing during prolonged starvation and exercise.

Conclusions:

• * Amino acids are significant oxidative substrates for trout, derived from diet or muscle protein.
• * Amino acids play a role in maintaining glucose levels during starvation and exercise in trout.
• * Alanine is not the most important glucogenic amino acid in trout, contrary to some contentions.