Measurement of early events in signal transduction beyond receptors involving G proteins function in mononuclear leucocytes

G protein function in human mononuclear leucocytes was measured through isoproterenol, carbamylcholine and dopamine-enhanced ³H-Gpp(NH)p binding. Dopamine and carbamylcholine exerted their effects through D₅ and M₂ receptors, respectively. ADP-ribosylation by bacterial toxins indicates that dopamine and isoproterenol affected G(s). while carbamylcholine affected G(i). Quantitative G proteins measures were conducted through immunoblot analyses with specific polyclonal antibodies against Gα(s), and Gα(i) subunits. Simultaneous functional and quantitative measures of G proteins showed significant correlations between function and immunoreactivities. Agonist-enhanced guanine nucleotide exchange is thus suggested as a method for measurement of early events in signal transduction beyond receptors in leucocytes, which can potentially serve for detecting alterations in G proteins measures in human disease.