RELEASE OF PROTEINS AND POLYSACCHARIDES FROM THE ALBUMIN GLAND OF THEFRESH-WATER SNAIL HELISOMA-DURYI - EFFECT OF CAMP AND BRAIN EXTRACTS

The albumen gland is a compound tubular exocrine gland found in the fe male reproductive tract of freshwater pulmonate snails such as Helisom a duryi. It secretes a perivitelline fluid, composed of protein and po lysaccharide complexes, and coats each fertilized egg. A 288-kDa nativ e glycoprotein, composed of several 66-kDa subunits, was identified in soluble extracts of albumen gland. Forskolin stimulates the release o f secretory granules, containing both proteins and polysaccharides, fr om the cytoplasm of the glandular cells. An acid extract of the centra l nervous system or the adenosine-3',5'-cyclic monophosphate (cAMP) an alogue 8-bromo cAMP, stimulates protein secretion from the gland. Pret reatment of the albumen gland with cAMP antagonist (R-p isomer of cAMP ) inhibits the stimulatory effect of a brain extract. Digestion of bra in extract with proteolytic enzymes abolishes its activity, suggesting the factor from the brain is peptidergic. The neuroactive agents sero tonin, Phe-Met-Arg-Phe-amide, Tyr-Gly-Gly-Phe-Met-Arg-Phe-amide, small cardioactive peptide B, and caudodorsal cell hormone were also tested for potential secretion-promoting ability. Brain extracts were partia lly purified with a Sep-Pak C-18 reverse-phase cartridge and indicate the peptide is relatively hydrophobic. These results suggest that a br ain peptide promotes the secretion of perivitelline fluid, and this is mediated by the adenylate cyclase/cAMP signal transduction pathway.