Studies on the uptake and metabolism of adenosine 3′:5′-cyclic monophosphate and N6,O2-dibutyryl 3′:5′-cyclic adenosine monophosphate in sea urchin eggs

Application of adenosine 3′: 5′-cyclic monophosphate (CAMP), N 6 , O 2′ -dibutyryl cyclic AMP (DBCAMP) or N 6 -monobutyryl cyclic AMP (N6-MBCAMP), from concentrations of 10 −7 to 10 −2 M had no effect on fertilization or cleavage rates in sea urchin eggs up to early gastrula stages. In order to study the permeability of CAMP and DBCAMP in sea urchin eggs, they were incubated with the nucleotides. CAMP was readily taken up by the eggs. There was no significant breakdown of the nucleotide in the extracellular medium, indicating that CAMP entered the cell as such and was not resynthesized from a metabolic breakdown product. When eggs were incubated with DBCAMP, no dibutyryl derivative could be recovered from egg-extracts, the compound having been converted to N 6 MBCAMP. Homogenates of the eggs similarly were able to deacylate DBCAMP, indicating the presence of a potent esterase activity. The intracellular levels of CAMP and N 6 -MBCAMP reached concentrations greater than 10 −5 M, at least two orders of magnitude higher than the CAMP level normally found in sea urchin eggs. These results indicate that CAMP does not participate in regulation of mitosis in early embryogenesis in sea urchin eggs.