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Trans‐stimulation of L‐system amino acid transport in normal and chronic leukemic human lymphocytes: Phorbol ester restores function in CLL
Author(s) -
Segel George B.,
Woodlock Timothy J.,
Lichtman Marshall A.
Publication year - 1988
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041340325
Subject(s) - chronic lymphocytic leukemia , phorbol , stimulation , intracellular , extracellular , amino acid , chemistry , biochemistry , microbiology and biotechnology , leukemia , biology , endocrinology , protein kinase c , immunology , enzyme
Chron c lymphocytic leukemia (CLL) B‐lymphocytes have a unique and specific diminution of L‐system (leucine favoring) amino acid uptake; the maximal velocity is approximately 10% of normal B‐lymphocytes. Treatment of CLL B‐cells with the maturational agent, tetradecanoyl phorbol acetate, results in restoration of L‐system amino acid uptake to normal velocity. To further characterize the effect of phorbol ester on the L‐system of CLL B‐cells, we have examined the ability of normal and CLL lymphocytes to exchange intracellular for extracellular amino acids by the L‐system (trans‐stimulation). A 60% increase in L‐system uptake was noted in normal B‐ and T‐lymphocytes in the presence of a high intracellular concentration of 2‐amino‐2‐carboxy‐bicycloheptane (BCH), a largely L‐system‐specific substrate. L‐system transport was not trans‐stimulated in CLL B‐lymphocytes. Phorbol ester treatment restored L‐system uptake in CLL to a normal V max of 900 umol/liter cell water per minute in the absence of BCH loading. The V max could be increased further to 2,400 if phorbol ester‐treated CLL cells were loaded with BCH. Hence, phorbol esters result not only in a normalization of L‐system uptake in CLL B‐cells but the transport system demonstrates exchange rates comparable to normal lymphocytes.