Nitrogen excretion and arginase activity during amphibian development

Abstract

The ratio of excreted NH3-N to Urea-N is approximately 9:1 in tadpoles of Rana temporaria up to 60 days old. This ratio decreases slowly during development of the hind limbs to 7:3 at the stage just previous to piercing of the membranes by the fore limbs. During the next 4 days a rapid decrease of NIL and increase in urea excretion occur, giving finally an N partition of 1:9, characteristic of the adult frog. Accompanying this transformation a rapid increase in arginase activity of the liver from practically zero value is observed. Liver wt. is also increased 3 times during metamorphosis and total output of NH3 and urea is doubled immediately after freeing of fore limbs.