Fate and distribution of kynurenic acid administered as beverage.

BACKGROUND: Kynurenic acid (KYNA) is a biologically active metabolite of tryptophan exerting action on several receptors located in the brain and periphery. KYNA can be synthesized endogenously or supplied in the diet. It was documented that KYNA is present in various types of food. However, its presence in beverages was not yet investigated. Here, we measured content of KYNA in tea and coffee as well as analyzed distribution and fate of intragastrically administered labelled KYNA in mice. METHODS: 16 and 13 studied samples of tea and coffee, respectively were of commercial origin. Tea and coffee infusions were prepared according to the producers' guidelines. KYNA content in beverages was measured by means of HPLC detection. Adult male mice were used for analysis of fate of intragastrically administered labelled KYNA and collected samples were analyzed using liquid scintillation counter. RESULTS: KYNA was identified in all studied beverages. Amounts of KYNA found in various types of beverages differed significantly. The highest content of KYNA in tea and coffee was 8.7 µg/100 ml and 0.63 µg/100 ml, respectively. It was found that KYNA administered intragastrically as a liquid is absorbed from the digestive system and readily excreted in urine. The atypical kinetics of KYNA distribution were found in intestinal content of cecum, where it appeared later and persisted longer than in other tissues. CONCLUSIONS: Our data show that tea and coffee intake may contribute to KYNA content in the human organism. The distribution pattern of KYNA delivered as a liquid suggests that it either directly affects digestive system's functioning and intestinal microbiome composition, or participates in the whole body pool of KYNA.

Subcellular distribution of the acidic ribosomal P-proteins from Saccharomyces cerevisiae in various environmental conditions.

The yeast ribosomal "stalk"--a lateral protuberance on the 60S subunit--consists of four acidic P-proteins, P1A, P1B, P2A and P2B, which play an important role during protein synthesis. Contrary to most ribosomal proteins, which are rapidly degraded in the cytoplasm, P-proteins are found as a cytoplasmic pool and are exchanged with the ribosome-bound proteins during translation. As yet, subcellular trafficking of P-proteins has not been extensively investigated. Therefore, we have characterized--using immunological approaches--the cellular distribution of P-proteins in several environmental conditions, characteristic of yeast cells, such as growth phases, and heat-, osmotic-, and oxygen-stress. Using the western blotting approach, we have shown P-proteins to be present in constant amounts on the ribosomes, despite their exchangeability with the cytoplasmic pool, and regardless of environmental conditions. On the other hand, P-protein level in the cytoplasm decreased sharply throughout the consecutive growth phases, but was not affected by several stress conditions. Applying the electron microscopic technique and immunogold labeling, we have found that P-proteins are located in two cell compartments. The first one is the cytoplasm and the second one--an unexpected place--the cell wall, where P-proteins are fully phosphorylated. Moreover, the existence of P-proteins on the cellular wall is not affected by various environmental conditions.