Membrane transduction pathway in the neuronal control of protein secretionby the albumen gland in Helisoma (mollusca)

The albumen gland in Helisoma secretes a perivitelline fluid which surround s each egg and is made up of several 66 kDa protein subunits and polysaccha ride complexes. Forskolin, an adenylate cyclase activator, stimulated the s ecretion and release of the perivitelline fluid. An acidic extract of the c entral nervous system increased the intracellular concentration of cAMP in the albumen gland and this results in the release of the 66 kDa molecule an d other proteins. Digestion of the brain extract with proteases abolished t his activity, suggesting that the factor is a peptide. Cyclic AMP analogues and IBMX also stimulated the protein secretion in dose-dependent manner. F orskolin when added with the brain factor had an additive response. SQ22536 , a non-competitive inhibitor of adenylate cyclase, inhibited brain extract dependent adenylate cyclase activity whereas aluminum fluoride, a G protei n activator, was found to stimulate adenylate cyclase. Dopamine also stimul ates protein secretion by the albumen gland and through the application of various agonists and antagonists of dopamine, it was established that the n eurotransmitter acts via D-1-like receptors by stimulating adenylate cyclas e.