FURTHER STUDIES OF THE EXCRETION OF ATROPINE-ALPHA-C¹⁴

¹ Pharmacology Branch, U. S. Army Chemical Center, Maryland

The rat and the cat, like the mouse, excrete C¹⁴ in the urine in large part as what may be unchanged atropine (with an R_f of 0.75 to 0.84). In one rat urine collected 6.5 hr. after atropine injection, about 1.4 per cent of the C¹⁴ in the urine was in the form of a tropic-acid-like compound (R_f 0.92). The substances responsible for the other chromatographically separable loci of C¹⁴ have not been identified even tentatively in this work. The most important of these loci of C¹⁴ in rat urine have R_f's of about 0.06, 0.19, 0.61 and 0.70.

The guinea pig excretes the C¹⁴ from labeled atropine primarily as "tropic acid," with "unaltered atropine" as a less important urinary excretion product.

In the rat, urinary excretions of C¹⁴ after i.v., i.m. or s.c. injections of labeled atropine were approximately the same. Urinary excretion of C¹⁴ after oral or i.p. administration of labeled atropine was about 70 per cent of the mean excretion with the first 3 routes of administration.

The liver, the kidney, the lung and the pancreas are the most important nonhollow organs in taking up the labeled material initially. The hollow organs which show the highest initial uptake of the C¹⁴ label are the duodenum and jejunum. There is a progressive movement of label down the intestinal lumen. The liver is thought to excrete products of atropine metabolism via the bile.

In the rat and the cat, unlike the mouse and the guinea pig, excretion of C¹⁴ in the feces is almost equal in importance to urinary excretion.