[Pharmacological effect of exogenous histones on muscles].

Different histone fractions contain sequences homologous to those of several regulatory peptides. All the histone fractions demonstrated dose-dependent positive chronotropic effect in spontaneously contracting rat atrial preparations. The range of their activity was as follows: H4 greater than H1 greater than H2a much greater than H3. Synthetic COOH-terminal histone H4 pentapeptide (historphin) Tyr-Gly-Phe-Gly-Gly demonstrated opioid activity by inhibiting electrostimulated guinea-pig ileal contractions. It is suggested that some biological activities of histones are related to the presence of regulatory peptide sequences in their structure.