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R Stengg

Publications and source records attributed to R Stengg.

6 recordsLinked to original sources
PubMed1978

Influence of hexobendine, dipyridamole, dilazep, lidoflazine, inosine and purine riboside on adenosine uptake by the isolated epithelium of guinea pig jejunum.

The uptake of (14C)adenosine by isolated epithelium of guinea pig jejunum, administered on the blood side, was inhibited by hexobendine, dipyridamole, dilazep and lidoflazine. On the lumen side, however, weak inhibition was observed with lidoflazine only and no significant change was recorded with hexobendine, dipyridamole or dilazep. This difference was not altered when the degradation of hexobendine by the jejunal epithelium was blocked by physostigmine. When adenosine uptake was already reduced by purine riboside, further addition of hexobendine, dipyridamole, dilazep or lidoflazine caused divergent changes depending on the side of administration. Adenosine uptake was further diminished on the blood side, but raised towards control values on the lumen side. By contrast, inosine inhibited adenosine uptake on both sides of the epithleium. The results suggest that the mechanism of adenosine uptake is different on either side with respect to inhibition characteristics, corresponding to differences in morphology and function of the two sides of the intestinal epithelium.

Adenosine↗
PubMed1977

Adenosine uptake by the isolated epithelium of guine pig jejunum.

The uptake of [8-14C]adenosine by the isolated epithelium of guinea pig jejunum was faster than that of inosine, hypoxanthine, or adenine. The initial velocity of adenosine uptake from both the luminal and the antiluminal side of the epithelium exhibited saturation kinetics. The apparent Km, V, and passive permeability of luminal adenosine uptake were all lower than the corresponding values of antiluminal uptake. p-Nitrobenzyl-thioguanosine inhibited adenosine uptake from both the luminal and the antiluminal side, whilst hexobendine decreased the uptake only from the antiluminal side of the epithelium. The results suggest that adenosine enters the intestinal epithelium by a carrier-mediated process in addition to passive diffusion. The antiluminal transport system for adenosine seems similar to that of other tissues with respect to hexobendine inhibition; the luminal transport mechanism, however, exhibits different properties, being insensitive to hexobendine.

Adenine↗
PubMed1977

Salvage of adenosine, inosine, hypoxanthine, and adenisine by the isolated epithelium of guinea pig jejunum.

The metabolism of adenosine, inosine, hypoxanthine, and adenine (labelled with 14C in the carbon 8 position) at a concentration of 5 X 10(-6) M was studied in isolated epithelium of guinea pig jejunum. When adenosine or adenine was added to the antiluminal side of the epithelium, two-thirds or one-half, respectively, of cellular radioactivity was incorporated into the nucleotide fraction, mainly in the form of adenine nucleotides. Nucleotides synthesis from inosine or hypoxanthine was significantly smaller than that from adenosine. By contrast, another metabolic patern was found after luminal administration of adenosine, inosine, or hypoxanthine: the incorporation rate into the nucleotide fraction was equally high and the label was recovered in IMP and adenine nucleotides to about the same extent with all three substrates. Purine riboside (10(-4) M) significantly depressed nucleotide formation from adenosine, with respect to IMP formation in particular, while no change was observed in inosine or hypoxanthine salvage. The results suggest compartmentation of the enzymes of purine metabolism within the intestinal mucosa. The significance of this conclusion with regard to the salvage pathway is discussed.

Adenine↗