Kinetics of ammonia production and excretion in the acidotic dog

¹ Department of Physiology and Biophysics, Cornell University Medical College, New York City

The Chinard technique of rapid injection into one renal artery of a glomerular marker (creatinine) and a compound whose utilization or excretion is under investigation has been employed in a study of the time courses of production and excretion of ammonia. Following the injection of N¹⁵H₄ Cl or amide-N¹⁵-labeled glutamine, the label appeared in the urinary ammonia within a partially corrected time interval of 11 sec or less, suggesting that, in both instances, the labeled ammonia entered the urine as far along the nephron as the convoluted portion of distal tubules and cortical collecting ducts. Creatinine appeared in the urine after a delay of 60–100 sec. Following injections of amino-N¹⁵-labeled glutamine, appearance of label in urinary ammonia was delayed about 20 sec relative to that observed following injection of amide-N¹⁵-labeled glutamine. The time course of disappearance of label from the urine suggests that deamidation of glutamine is not rate-limiting for ammonia production and excretion, whereas deamination of glutamine may well be.

Note:
With the Technical Assistance of J. C. de Haas

Key Words: N¹⁵ glutamine • N¹⁵ ammonia • metabolism of glutamine • precursors of ammonia

Submitted on June 4, 1965