Expression of glucagon receptors on T- and B- lymphoblasts: comparison with insulin receptors

Abstract

Activation of T- and B-lymphocytes by a variety of immunological stimuli has been reported to induce specific insulin receptors. The purpose of the present work was to determine whether glucagon receptors are also induced in activated cells. Studies of glucagon and insulin receptors were carried out using normal human mononuclear cells activated by phytohemagglutinin or T-cell growth factor (TCGF), as well as established B- and T-lymphoblastoid cell lines. With phytohemagglutinin, glucagon and insulin binding increased 15- and 36-fold, respectively, and peaked after 5 days in parallel with the rise in thymidine incorporation. Increased binding was associated with an increase in the number of receptors, most marked for insulin, though affinity for the insulin receptor was decreased. Normal human mononuclear cells cultured with TCGF showed an early modest rise in insulin binding due to increased receptor number, without a change in affinity, and a striking and progressive rise up to 50-fold in glucagon binding due to both increased receptor number and affinity. The differences in receptor response to these T-cell mitogens suggest that TCGF selects out a T-lymphoblast subset with very high glucagon receptors. B- and T-lymphoblastoid cells showed patterns of glucagon and insulin receptors that appear to be characteristic for each cell type. Glucagon binding was 7-fold higher (P less than 0.01), while inulin binding was 7-fold lower (P less than 0.01) in T- vs. B-lymphoblastoid cells. T-Cell lines had twice the number of glucagon receptors, whereas B-lines had 4-fold the number of insulin receptors, with much greater affinity for insulin compared with T-line insulin receptors. Induction of both insulin and glucagon receptors on activated lymphoblasts suggests that these receptors may play a significant role in cell function.