Cyclic GMP levels during regeneration in Hydra oligactis and its distribution in steady‐state animals

Abstract

AbstractTo assess the involvement of cyclic guanosine 3′, 5′‐monophos‐phate (cGMP) in regulating cell division versus cell differentiation in regenerating systems, a radioimmunoassay study of the distribution and concentration of cGMP in steady‐state and regenerating Hydra oligactis was undertaken. In steady‐state animals, uniformly low cGMP levels were observed in the hypos‐tome‐tentacle, and upper‐, mid‐, and lower‐gastric regions. The peduncle/basal disc region, however, evidenced markedly higher levels of this cyclic nucleotide. Removal of the animal's interstitial cell population, using nitrogen mustard, did not alter this distribution. Animals lacking interstitial cells, however, exhibited greater concentrations of cGMP/cell than did untreated controls. During distal, whole animal regeneration increased cGMP concentrations were noted during wound healing and 3 hr antecedent to tentacle elaboration. A similar pattern was observed in the distal 1 mm of regenerating tissue. Basal disc regeneration was accompanied by only a single elevation in cGMP levels, concomitant with basal disc reformation. Wounded, but nonregenerating, animals likewise showed only a single rise in cGMP levels; this increase occurred during wound healing. The data, therefore, are consistent with changes in cGMP concentrations occurring in association with periods of DNA synthesis (e.g., tentacle elaboration and restructuring of the wounded surface). The distribution data and nitrogen mustard studies allow the further conclusion that the changes in cGMP recorded reflect activities of the epithelial cell population.