[Changes in the sensitivity of developing sea urchin embryos to prostaglandin F2alpha and cyclic 3',5'-adenosine...

It was shown that at various stages of the first mitotic cycles the developing ova of Strongylocentrotus intermedius displayed a different sensitivity to toxic concentrations of prostaglandin F2alpha and to cyclic 3',5'-adenosinmonophosphate (cAMP). The differences in the sensitivity to each of these substances were regular and similar in character and depended on the time lapse after the completion of division next in turn. There were revealed two periods of increased sensitivity of the ova--the first one--during the 20th minute after the completion of each division--to both substances, and the second one--during the 40th minute--to cAMP, and during the 50th minute--to prostaglandin F2alpha.