| Abstract: | Cow red cell glycolysis, which can be stimulated by a variety of purines and pyrimidines, was also found to be elevated by its own plasma. Dialyzed or charcoal-treated plasma could no longer stimulate glycolysis, suggesting that the stimulating factors may be purines or pyrimidines. Determination of purines or pyrimidines in plasma revealed the presence of xanthine (0.31 muM), hypoxanthine (0.60 muM), and adenosine (0.05 muM), as well as unknown compounds. A physiologic level of hypoxanthine, with or without xanthine and adenosine approximating their concentrations in plasma, resulted in the stimulation of cow red cell glycolytic rate by 16% (P less than 0.01). These findings suggest that plasma-borne purines may act on cow red cells in concert with as yet unidentified factors. Moreover, exchanging calf and cow plasmas produced no stimulatory effect on either calf or cow red cell glycolysis, suggesting that a) calf red cells lack some of the cellular components that respond to this stimulator and, b) only cow plasma contains this specific stimulator. In other species, including dog, cat, rabbit, rat, guinea pig, and human, stimulation of glycolysis by plasma was not observed. |
