[Origin and fixation of pyrophosphates in the parietal bones of young rats].

Calvaria from 6 to 13-day-old rats mineralize and bind pyrophosphates which are transferred from nucleotides, as shown by : 1 -- the increase of pyrophosphates in young rat calvaria incubated with nucleoside triphosphate, especially ATP ; 2 -- the more important increase of pyrophosphate content when ATP is renewed in the incubation medium ; and 3 -- binding of [32P] pyrophosphate [beta 32P] ATP. The effect of preheating of calvaria on 32P binding from [beta32P]ATP led us to assume that two systems might be involved in pyrophosphate fixation : a heat-labile, non-specific, phosphatase system, and a heat-stable pyrophosphotransferase system. cAMP increases the pyrophosphate content of calvaria incubated with ATP : that effect may result from either an inhibition of the phosphatase system, or an activation of the pyrophosphotransferase system.