Effect of adenosine 3′,5′-monophosphate on melanin dispersion in the shore crab Carcinus maenas (L)

Abstract

The mode of action of the melanin-dispersing hormone (MDH) in the shore crab Carcinus maenas was studied. The dose-response relationship for this hormone obtained from the sinus gland was compared to the response of the melanophores to injected adenosine 3′,5′-monophosphate (cyclic AMP). In agreement with data reported on the effect of cyclic AMP on amphibian melanophores, millimolar concentrations of this nucleotide were required to cause melanin dispersion in the crab. Although the activity of adenyl cyclase in epidermal preparations of the shore crab was increased about 8-fold when fresh sinus gland extracts were added to the incubation medium, this stimulation does not appear to be related to the MDH activity of these extracts. These findings are discussed with reference to the concept that the action of MDH on the melanophore may be mediated by cyclic AMP.