Somatostatin receptors on human lymphocytes and leukaemia cells

Receptors for somatostatin were identified on mitogen-activated human peripheral blood lymphocytes (PBL) and human leukaemic cells in 87.5% of lymphoblastic leukaemia and in 12.5% of non-lymphocytic leukaemia, using a somatostatin radiobinding assay. The specific binding of 125I-somatostatin of these cells increased linearly with the cell numbers and was suppressed by non-iodinated somatostatin. We investigated the distribution of fluorescent somatostatin to mitogen-activated PBL by using a fluorescence-activated cell sorter (FACS). Over 95% of the cell populations bound fluorescent somatostatin and no distinct predilection was found among certain lymphocyte subpopulations and somatostatin receptor-positive cells. Scatchard analysis showed a single class (low affinity) of binding site on mitogen-activated PBL and two classes (high and low affinity) of specific binding sites on lymphoblastic leukaemia cells.