Role of the small intestine in glutamine metabolism

The absorption, tissue distribution and excretion of enteraly administered alpha-ketoglutarate in rats

The absorption, tissue distribution and excretion of enteral alpha-ketoglutarate (AKG) was studied in four experiments. Six male Sprague Dawley rats were used to investigate the excretion of AKG in urine and faeces. Thirty rats, randomly assigned to five groups, were used to investigate the distribution of AKG in body tissues. They were gavaged with AKG enriched with 3 muCi/kg BW of (14)C uniformly marked AKG. Fourteen male Sprague Dawley rats were used to study the absorption of AKG (duodenum vs. ileum). Intestinal recovery of NaAKG vs. CaAKG was investigated in 36 rats. There was no significant excretion of non-metabolized AKG in the urine and faeces. There was no significant difference in the systemic levels of AKG when comparing the proximal to distal small intestine infusion. Up to 50%, 30% and 20% of gastrically delivered AKG was recovered in the stomach, 0.5, 1 and 2 h after gavage; the jejunal recovery achieved a maximum of 3%, 30 min after gavage, and was not detectable 2 h later. There was a relatively high distribution of (14)C-AKG in the tissues (e.g. liver, brain, bones, skin, muscles), 3 h after gavage, up to 70% of the administered dose. In conclusion, the high rate of retention of the carbon from AKG allows the postulation that there is a non-energetic mode of metabolism of intragastrically administered AKG. After conversion to final metabolites, AKG penetrates into all tissues and organs of rats, including the bone tissue. Intestinal absorption of AKG does not depend on the type of AKG salt administered.