Postnatal behaviour of guanase activity in rat tissues.

The behaviour of guanase activity and the 8-azaguanine/guanine deamination ratio of rat tissues during postnatal development were studied. In the liver and brain, the enzymatic activity, present from birth, gradually increases up to the 4th week. In the kidney, guanase activity appears after the 1st week and reaches the level found in adult tissues after the 6th week. The value of the deamination ratio of tissues at birth is higher than that of adult animal tissues.