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 H-3-Gpp(NH)p binding. Dopamine and carbamylcholine exerted their effects through D-5 and M(2) 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 G alpha(s), and G alpha(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.