The head activator is released from regenerating Hydra bound to a carrier molecule

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Abstract
Hydra forced to regenerate a head releases head activator and head inhibitor during the first hours after cutting to induce head‐specific growth and differentiation processes. Analysis of the size distribution demonstrated that the head‐activator peptide is co‐released with (a) large molecular weight carrier molecule(s) to which it is non‐covalently bound. The carrier‐bound head activator is fully active on Hydra indicating that a carrier does not hinder the interaction with receptors. In contrast to this the head inhibitor is released in its naked, low molecular mass form. The association or non‐association with a carrier molecule results in marked differences in biological properties. The head activator has a short range of action, but a long half‐life, the head inhibitor has a global range of action, but a short half‐life. These results provide a plausible explanation why two antagonistically acting substances, although they are released from the same site and simultaneously nevertheless can give rise to a well‐defined temporal and spatial pattern of differentiation as occurs, for example, during head regeneration in Hydra.