Phorbol 12‐myristate 13‐acetate modulates the cAMP‐induced light‐scattering response of a Dictyostelium discoïdeum cell population

Abstract

The effect of phorbol 12‐myristate 13‐acetate upon the light‐scattering response to cAMP of a D. discoïdeum cell suspension was investigated. It was found that the first spike of the cAMP‐mediated light‐scattering change (peaking at about 15–20 s after stimulation) was inhibited by the phorbol ester. This effect was concentration dependent with an half‐maximum value for the inhibition of 4 nM. The inhibition was found to be maximal after a 10–20 min incubation time. The phorbol ester was shown to affect the dose‐response relationship between the cAMP concentration and the relative amplitude of the light‐scattering change, more by decreasing the number of cAMP receptors than by decreasing their apparent affinity for cAMP.