Purine metabolism in cultured aortic and coronary endothelial cells

Abstract

Purine salvage pathways in cultured endothelial cells of macrovascular (pig aorta) and microvascular (guinea pig coronary system) origin were investigated by measuring the incorporation of radioactive purine bases (adenine or hypoxanthine) or nucleosides (adenosine or inosine) into purine nucleotides. These precursors were used at initial extracellular concentrations of 0.1, 5, and 500 microM. In both types of endothelial cells, purine nucleotide synthesis occurred with all four substrates. Aortic endothelial cells salvaged adenine best among purines and nucleosides when applied at 0.1 microM. At 5 and 500 microM, adenosine was the best precursor. In contrast, microvascular endothelial cells from the coronary system used adenosine most efficiently at all concentrations studied. The synthetic capacity of salvage pathways was greater than that of the de novo pathway. As measured using radioactive formate or glycine, de novo synthesis of purine nucleotides was barely detectable in aortic endothelial cells, whereas it readily occurred in coronary endothelial cells. Purine de novo synthesis in coronary endothelial cells was inhibited by physiological concentrations of purine bases and nucleosides, and by ribose or isoproterenol. The isoproterenol-induced inhibition was prevented by the beta-adrenergic receptor antagonist propranolol. The end product of purine catabolism in aortic endothelial cells was found to be hypoxanthine, whereas coronary endothelial cells degraded hypoxanthine further to xanthine and uric acid, a reaction catalyzed by the enzyme xanthine dehydrogenase.

Purine salvage to adenine nucleotides in different skeletal muscle fiber types

“…Because the salvage precursor obligatorily passes through the vasculature to reach the myocytes, considerable metabolism by the vascular endothelium could act as a barrier and impact salvage measurements. Indeed, cultured endothelial cells are capable of purine salvage and de novo synthesis (9). Although skeletal muscle endothelial cells have been implicated in transport and metabolism at micromolar concentrations of purines in perfusion studies (12), we suspect that purine metabolism by the endothelium would become quantitatively less important at the higher precursor concentrations used here.…”

Serum uric acid is associated with microvascular function in hypertensive individuals

“…[24][25][26] This has motivated investigation of the effects of xanthine oxidase inhibitors on microvascular endothelial function. In animal models, allopurinol preserves microvascular endothelial function and blood flow in mesenteric vessels after resuscitation from haemorrhagic shock, 27 suggesting that xanthine oxidase may contribute to ischaemia reperfusion injury and associated endothelial dysfunction in this setting.…”

CoCl2-Mimicked Endothelial Cell Hypoxia Induces Nucleotide Depletion and Functional Impairment That Is Reversed by Nucleotide Precursors

“…Another strategy for replenishing the intracellular ATP pool in ECs is to reinforce its re-synthesis [ 61 ]. The restoration of purine nucleotides can be accomplished from precursors, such as amino acids, formate or bicarbonate, by the multipart de novo pathway or by salvage pathways from purine derivative precursors, bases and nucleosides [ 62 ].…”