| Abstract | In rat liver following partial hepatectomy an unprecedented biphasic increase in cyclic AMP concentration was observed. After a lag period of 112hr, the cyclic AMP content rose to a peak at 212hr. The cyclic AMP level fell to normal at 8 hr, and then rose again to a second peak at 12 hr. DNA synthesis started at 18 hr, by which time the cyclic AMP level was approaching control values. A biphasic increase in cyclic AMP concentration was also observed to precede the initiation of DNA synthesis in intact liver following the infusion of a mixture of tri-iodothyronine, amino acids, glucagon and heparin. The relationship between these biphasic changes in cyclic AMP levels and the initiation of DNA synthesis in liver is discussed. |
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