Effect of glutathione on cyclic nucleotide levels in hydra attenuata

1. 1. The concentrations of cyclic adenosine 3′:5′ monophosphate and cyclic guanosine 3′:5′ monophosphate have been measured in Hydra attenuata before and during exposure to glutathione, a natural activator of the feeding response in this animal. 2. 2. Levels of cGMP are consistently elevated in the presence of glutathione at concentrations of 2 × 10^-8 M and above, while no consistent changes in cAMP levels can be measured. 3. 3. The increase in cAMP concentrations found in the presence of glutathione is also observed in the presence of an active glutathione analog and is blocked by the feeding response inhibitor, glutamate. 4. 4. The time course and concentration dependence of the effect of glutathione on cyclic nucleotide levels suggest that neither cAMP nor cGMP mediates the effects of glutathione on hydra feeding behavior.