Studies into disturbing receptor 'memory' in a unicellular (Tetrahymena) model system: changes in the imprinting potential on exposure to combinations of related and unrelated hormones.

Signal molecules (hormones) can induce a hormonal imprinting in the unicellular Tetrahymena, as judged from an increase in binding capacity on reexposure in the subsequent generations. Structurally unrelated polypeptide hormones (insulin, FSH) neutralize each other's effect, whereas related hormones (TSH-FSH) may amplify or depress it. The non-signal polypeptide molecule BSA prevents hormonal imprinting on combined exposure. The glucocorticoid hormone enhances binding capacity for insulin (as in mammals) and increases its imprinting potential, whereas on TSH and FSH it has no similar effects. The amino acid hormone serotonin increases the binding capacity for TSH and FSH in non-pretreated cells, but depresses rather than stimulates the imprinting potential of these hormones, measured in the case of the second encounter.