328 E. LUNDSGAARD VOL. 4 (1950) 



related to the observation made by many investigators^' *» ^' «» ' that the respiration of 

 tissue slices is higher and more stable in serum than in Ringer solution. Though this 

 observation is not absolutely identical with those of the writer, it appears most probable 

 that the substance (or substances) in serum which enchances tissue respiration is the 

 same as the substance (or substances) which is gradually removed from the blood by an 

 isolated liver causing a decline in the rate of oxidations. The question of the nature of 

 the serum constituents which enchance tissue respiration has been delt with in a rather 

 explicit manner by Warren in two publications. In the first of these^ it has been demon- 

 strated that the stimulating effect of serum on tissue respiration partly can be attributed 

 to its bicarbonate content. According to Warren the maximal effect of adding bicarbon- 

 ate to a Ringer-phosphate medium is obtained at a concentration of only 3 mM per liter. 

 Variations in the bicarbonate concentration at higher levels are without any influence 

 on the rate of oxidations. Since whole blood under constant and fairly high carbon 

 dioxide pressure has been used in the experiments described one can certainly rule out 

 changes in bicarbonate content as being responsible for the observed changes in oxygen 

 uptake in the isolated liver. 



In accordance with Canzanelli et al.^, Warren finds substances capable of 

 enchancing the respiration of tissue slices in the ultrafiltrate of serum. Only about 50% 

 of the effect can be attributed to bicarbonate. In his second paper Warren^ reports 

 attempts to fractionate serum with respect to its action in enchancing tissue respiration. 

 From his elaborate experiments Warren concludes that lactic acid and amino acids 

 are not involved in the stimulating effect of serum on tissue respiration. I draw the 

 same conclusion from my observations. Warren further suggests that the active 

 substance is a dicarboxylic acid, but he has not put this assumption on a direct trial by 

 adding dicarboxylic acids to the Ringer-phosphate medium used in his experiments. 

 In my experiments I have tested different organic acids assumed to be formed as inter- 

 mediates in tissue metabolism. However, no effect on the low oxygen uptake of the 

 isolated liver was observed. 



SUMMARY 



Observations are presented indicating that the normal metabolic rate of the liver is dependent 

 on a substance (or substances) formed in the extrahepatic tissues and carried to the hver through 

 the blood. This still unidentified substance is used or destroyed in the hver tissue. 



RfiSUMfi 



L'auteur prdsente des observations indiquant que la vitesse normale du metabolisme du foie 

 depend d'une substance (ou de substances) form^e dans les tissus extrah^patiques et qui est amenee 

 au foie par le sang. Cette substance non encore identifi(5e est utilisee ou detruite dans le tissu h6pa- 

 tique. 



ZUSAMMENFASSUNG 



Beobachtungen werden beschrieben die darauf hinweisen, dass die Normalgeschwindigkeit des 

 Lebermetabolismus von einer Substanz (oder von Substanzen) abhangt, die in ausserhalb der Leber 

 gelegenen Geweben gebildet und durch das Blut der Leber zugefuhrt wird. Diese noch nicht identifi- 

 zierte Substanz wird im Lebergewebe verbraucht oder zerstort. 



References p. 32^. 



