Specific high affinity cell membrane receptors for biologically active phorbol and ingenol esters

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Abstract
A variety of normal and transformed avian and mammalian cells and tissues contain high affinity specific receptors on their membranes which interact with biologically active phorbol and ingenol esters in a reversible and saturable manner. The binding of labeled phorbol-12,13-dibutyrate (PDBu) to live or glutaraldehyde-fixed cells is dose-, time- and temperature-dependent. Those phorbol or ingenol esters which stimulate cell growth in culture and have tumor-promoting activity in vivo inhibit the binding of labeled PDBu, while the biologically inactive derivatives fail to do so. Other non-diterpene tumor-promoting agents, epidermal growth factor (EGF), retinoids and prostaglandins do not compete for the binding of labeled PDBu to its specific membrane receptors.