The metabolism of 14C-labelled bicarbonate in the cat

Abstract

Apparatus and technics are descr. for in vivo studies of the metabolism of C14-labelled bicarbonate in the cat. The rate of expiration of COl42 after intraven. injn. of NaHCO143 is initially very rapid, 50% being expired in the 1st 30 min., the total expired in 5 hrs. being 79-81% of the injd. Cl4. The rate of expiration can be represented by an exponential equation with 3 compounds of half-lives 2.85, 29.6 and 582 min. respectively. Of the Cl4 injd., 3.1% was incorporated into urea in 5 hrs., 50% of this incorporation occurring in the 1st 30 min. Within the exptl. error (+ 2%) all the urea C synthesized was derived from C in rapid equilibrium with blood bicarbonate. After 4 hrs. 6% of the injd. Cl4 was present in bone, the C of which exchanges relatively slowly with blood bicarbonate. The blood, muscles and viscera contained approx. 1% of the isotope at that time. These results show that the bicarbonate pool is not homogeneous, but consists of several component CO2-exchange mechanisms operating at widely differing rates.