Oligopeptide fragments of the enkephalin molecule interfere with hematopoietic cell colony formation.

Dipeptide Tyr-Gly and tripeptide Tyr-Gly-Gly representing the NH(2)-end of the Met-enkephalin molecule inhibited the GM-colony formation in clonal cultures of mouse bone marrow cells. Intermediate or C00H-terminal dipeptides Gly-Gly and Phe-Met respectively were inneffective. The suppressive effects were not abolished by opioid receptor blocking agent naloxone and only partly so by depletion of the accessory (adherent) cells. The results are congruent with idea that neuropeptides and products of their enzymatic degradation participate in the regulation of hematopoiesis.