Characterization of (-)-[3H]dihydroalprenolol binding to intact and broken cell preparations of human peripheral blood lymphocytes.

In this study we compared characteristics of (-)-[3H]dihydroalprenolol ([3H]DHA) binding sites in crude membrane preparations of human peripheral blood lymphocytes with those of intact, viable cells. A valid determination of specific beta-adrenergic receptor binding in both preparations was obtained by defining non-specific [3H]DHA binding with 10(-6) M l- or dl-propranolol or 10(-3) M l-isoproterenol. Higher concentrations of propranolol were used in prior reports on lymphocyte membranes. We showed that these concentrations may inhibit non-specific binding, causing non-saturability and inhomogeneity of the estimated 'specific' binding. In the intact cell preparations, inclusion of 10(-4) M phentolamine was necessary to reduce the high degree of non-specific binding. By contrast, phentolamine (10(-4) M) showed no effect on the [3H]DHA binding to membrane preparations. At 37 degrees C the [3H]DHA binding to beta-adrenergic receptor sites in both intact and broken cell preparations was rapid and reversible. The sites were stereoselective, as l-propranolol was about two orders of magnitude more potent to inhibit [3H]DHA binding than was the d-isomer. In both preparations, agonists competed for specific binding with a rank order of potency isoproterenol greater than epinephrine greater than norepinephrine, which indicated a beta 2-type of adrenergic receptor. The specific [3H]DHA binding was saturable and Scatchard analysis revealed comparable numbers of homogeneous, non-cooperative binding sites (approximately 1250 receptors/cell in the membrane preparations and 1700 receptors/cell in the intact cells). In spite of these similarities the membrane sites showed a lower affinity for the antagonists [3H]DHA and propranolol than did the intact cell sites, whereas their affinity for the agonists was increased. These differences indicate that the membrane system might be less suited to provide physiologically significant information about the beta-adrenergic receptor system.

Desensitization of the beta-adrenergic receptor on leucocytes after long-term oral use of a beta-sympathicomimetic; its effect on the beta-adrenergic blockade hypothesis of Szentivanyi.

Development of beta-receptor desensitization in leucocytes of asthmatics and normals during oral therapy with terbutaline was established by means of in vitro stimulation with terbutaline and isoproterenol. This desensitization disappeared about one week after oral therapy was discontinued. In addition no difference in stimulation pattern, measured as increase in intracellular c-AMP content, was determined between asthmatics and normals when both were not receiving therapy. Even when the asthmatics showed strong bronchial hyperreactivity no difference was found. These results do not support the beta-adrenergic blockade hypothesis of Szentivanyi.

Reutilization of 125I-labelled anti-IgE antibody and paper discs in PRIST and RAST IgE determination.

In the paper radioimmunosorbent test (PRIST) anti-human IgE coupled paper discs are used for the estimation of total IgE in blood serum: in the radioallergosorbent test (RAST) allergen-coupled paper discs are used for the estimation of specific IgE in blood serum. The bound IgE or specific IgE is quantified by a 125I-labelled anti-human IgE. The non-bound 125I-labelled anti-human IgE can be collected and used in new assay. By a 4-h incubation of the used paper discs with 1 M glycine-HCl buffer (pH 2.7) the IgE-labelled anti-IgE complex can largely be removed. The paper discs treated in this manner can be used in a new assay.