Inhibitory effect of dibutyryl cyclic AMP on the release of calcium, inorganic phosphate and lysosomal enzymes from calvarial bones cultured for 24 hours.

The effect of N6,O2'-dibutyryl adenosine 3',5'-cyclic-monophosphate (dbcAMP) on the mobilization of calcium (Ca2+), inorganic phosphate (Pi) and lysosomal enzymes was studied in a bone culture system for 24 h using half calvaria from 6--7 day-old mice. DbcAMP inhibited spontaneous as well as parathyroid hormone-stimulated mineral mobilization. DbcAMP in a concentration of 5 x 10(-4)M also reduced the activities of beta-glucuronidase, beta-galactosidase and acid phosphatase found in the media while the activities of lactate dehydrogenase, aspartate aminotransferase and alanine aminotransferase were not affected. It is concluded that cAMP is not a stimulator but an inhibitor of bone resorption within the culture period studied (24 h) and that the cyclic nucleotide might interfere with release processes involved in bone resorption.