title: Cyclic nucleotide metabolism during amphibian forelimb regeneration : I. The cyclic AMP phosphodiesterases.
abstract: Concentrations of the cyclic nucleotides in regenerating limb tissues change in a manner which suggests that they might mediate neural or endocrine influences upon specific developmental events. Since modulation of the role of cAMP within this process can be achieved through cAMP phosphodiesterase, enzymatic activity, relative intracellular distribution, and the kinetic parameters of this enzyme were examined at several stages of limb regeneration in adultNotophthalmus viridescens. Both forms of the phosphodiesterase displayed decreased activity about the time of bud formation. Total phosphodiesterase activity was reduced between 66% and 85% (as compared to intact limbs) between wound healing and palette stages. Relative intracellular distribution (soluble vs. particulate), however, remained essentially constant, 93%-98% soluble for the highKmform and 61%-71% soluble for the lowKmform of the enzyme, throughout this process. The apparentKmof the highKmform increased more than 2-fold during wound healing then fell to approximately 10% (0.7-1.1 μM) of the value of intact limbs (8.3 μM) during dedifferentiation and bud formation. A return to pre-amputational levels was subsequently achieved. In contrast, the apparentKmof the lowKmform increased (from 0.064 to 0.86 μM) during dedifferentiation and began decreasing thereafter. These results are consistent with the hypothesis that one or more mechanisms are operating to modify either the quantity, activity, or physical characteristics of the cAMP phosphodiesterases and that such changes are instrumental in regulating endogenous concentrations of cAMP in limb tissues during regeneration.
authors.affiliation: Department of Biology, Boston College, 02167, Chestnut Hill, Massachusetts, USA.
authors.forename: Janet M
authors.initials: JM
authors.lastname: Carroll
authors.affiliation: Department of Biology, Boston College, 02167, Chestnut Hill, Massachusetts, USA.
authors.forename: Raymond E
authors.initials: RE
authors.lastname: Sicard
keywords: Cyclic AMP; Notophthalmus viridescens; Phosphodiesterase; Regeneration