Suitability of oligopeptides for induction of hormonal imprinting—implications on receptor and hormone evolution

Hormonal imprinting induced in Tetrahymena and in Chang liver cells with di-, tri-, tetra- and pentapeptides (synthetic opioids and their fragments) has shown that both cell types are able to differentiate the related molecules from one another. The dipeptide phenylalanine + proline induced a measurable imprinting in the liver cells, and chain length increase, especially terminal coupling with tyrosine enhanced the imprinting potential enormously. Intra-chain changes in the amino acid sequence had a measurable effect on the intensity of imprinting. The molecules showing the relatively strongest physiological action accounted for the most intensive imprinting in both cell types; this indicates that, in all probability, induction of binding site formation plays a key role in the development of signal molecules, and thereby in hormone evolution.