The elevation of cAMP levels by a putative diuretic hormone in the osmoregulatory organs of the freshwater snail Helisoma duryi

Abstract

In the freshwater snail Helisoma duryi, the kidney and mantle are major organs for osmoregulation and the visceral ganglion is the putative source of diuretic hormone. The role of cAMP as a second messenger in hormonal regulation of these organs has been studied. Hypo-osmotic treatment of snails raised the levels of intracellular cAMP in their kidney and mantle tissues. Forskolin, isobutylmethylxanthine, and theophylline also increased the levels of intracellular cAMP in these tissues. In addition, when these tissues from snails that were acclimated in isosmotic medium were treated in vitro with extracts of visceral ganglion of snails that were acclimated in hypo-osmotic medium, elevated levels of cAMP were observed, 12-fold for the kidney tissue and 4-fold for the mantle tissue. The stimulatory substance from the visceral ganglion was heat stable but labile to proteolytic digestion. In similar in vitro experimental conditions, hemolymph taken from hypo-osmotically treated snails also raised levels of cAMP. It is suggested that in H. duryi cAMP is involved as a second messenger for hormonal osmoregulation by kidney and mantle, and that the putative diuretic hormone is a neuropeptide.