6-hydroxymethylpterin and 2-amino-4-hydroxy-6-formylpteridine

The transport routes used by CCRF-CEM human lymphoblastoid cells for the influx and efflux of unconjugated pteridines were analyzed using [3H]6-hydroxymethylpterin as a model compound. Influx proceeds by a mechanism that exhibits a Km of 66.7 microM and a Vmax of 0.077 nmol/min per mg cellular protein. The process is somewhat sensitive to metabolic inhibitors, particularly uncouplers of oxidative phosphorylation, and is significantly affected by the presence of other pteridines in the extracellular medium. The results suggest that pterins with either no 6-substituent (pterin) or those with methyl, hydroxyl, or formyl groups in this position, which exhibit Ki values between 25 and 77 microM, may share the same pathway for uptake. 6-Carboxypterin exhibits low affinity for the system (Ki greater than 500 microM), as do 7-substituted and 6,7-di-substituted derivatives and compounds with larger groups at the 6-position, such as neopterin and biopterin (Ki = 250-300 microM). Efflux of [3H]6-hydroxymethylpterin occurs rapidly and can proceed by at least two routes. The first, comprising approximately 50% of total efflux, is inhibited by extracellular pterins and exhibits similar properties to the uptake system in both its pattern of sensitivity to metabolic inhibitors and its specificity for pteridine structure. The route by which the remaining efflux occurs is relatively insensitive to metabolic inhibition. Adenine significantly inhibits 6-hydroxymethylpterin influx and efflux (Ki = 10.6 microM for uptake) but does not appear to share the same transport system. Similarly, methotrexate and folic acid exhibit little affinity for the unconjugated pteridine transport routes.

Topics: Biological Transport; Carbon Radioisotopes; Cell Line; Chromatography, Gel; Chromatography, High Pressure Liquid; Dose-Response Relationship, Drug; Humans; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Pteridines; Pterins; Tritium; Tumor Cells, Cultured

Lectin stimulation of human peripheral blood mononuclear cells causes an increase in neopterin, biopterin, 6-hydroxymethylpterin and 6-formylpterin, as was determined by HPLC after iodine oxidation of the acid extract. After 72 h, pteridines peak at levels 5-10 fold as compared to resting cells. Levels decline to initial values during the following 24 h. Changes in pteridine proportions indicate that the synthesis of tetrahydrobiopterin proceeding from dihydroneopterin triphosphate is controlled during the process of lymphocyte activation. The release of both cellular neopterin and biopterin, but not of 6-hydroxymethylpterin and its aldehyde, is controlled by interferon-gamma.

Topics: Animals; Biopterins; Chromatography, High Pressure Liquid; DNA Replication; Humans; Interferon-gamma; Iodine; Mice; Monocytes; Neopterin; Pteridines; Pterins; Time Factors

After iodine oxidation, biopterin, 6-hydroxymethylpterin, and 6-formylpterin were identified in mouse spleen lymphocytes by means of reverse-phase HPLC, Crithidia assay, and oxidative degradation. Concanavalin A activation induces a 30-fold increase in the pteridine amounts; biopterin as well as the sum of the carbinol and the aldehyde attain levels of 6-8 X 10(-12) mol/10(6) cells. The most rapid increase occurs during the first 24 hr. Thus, pteridine accumulation precedes the period of lymphocyte proliferation; maximum DNA synthesis was found after 72 hr. Biopterin remains largely inside the cells, whereas 6-hydroxymethylpterin and 6-formylpterin were found in the supernatant if the stimulated cells were subsequently incubated in a phosphate buffered salt solution (PBS). Isoxanthopterin was found in the PBS supernatant of control cells that previously were kept in medium alone rather than subjected to lectin stimulation. Only minimal amounts were found inside these cells, and this pterin was absent from the stimulated lymphocytes. The early increase in cellular pteridines and their differential release may well provide the basis for their modulating effect on interleukin-2 activity (Ziegler I, et al: Lymphokine Research 3:284, 1984).

Topics: Animals; Biopterins; Concanavalin A; In Vitro Techniques; Kinetics; Lymphocyte Activation; Lymphocytes; Male; Mice; Mice, Inbred Strains; Pteridines; Pterins; Spleen; Xanthopterin