Absorption and excretion of pyrrolizidine (Senecio) alkaloids and their effects on mineral metabolism in rabbits.

Abstract

A metabolism study was conducted with rabbits to determine the effect of consumption of 5% dietary Senecio jacobaea (SJ) on tissue mineral levels and mineral excretion. Gastro-intestinal (GIT) absorption of pyrrolizidine alkaloids (PA) from SJ was also studied by monitoring excretion into urine and feces and by the use of ligated gut segments in vitro. Inclusion of SJ into a diet containing added Cu (100 ug/g) and Zn (100 ug/g) caused a 2.6-fold increase in liver Cu concentration (P less than .05), decreased total liver Zn (P less than .05), and increased plasma Fe (P less than .05) when compared with rabbits consuming the same diet without SJ. Fecal and urinary excretion of Cu and Zn were not markedly affected by the addition of Cu, Zn and(or) SJ to rabbit diets. Excretion of PA from SJ in the diet was not affected (P greater than .05) by the addition of Cu and Zn to the diet. The PA elimination was much greater in urine than feces (P less than .001). Isolated PA from SJ were found to be readily transferred across the mucosa of isolated everted sacs of jejunum and ileum in vitro against a concentration gradient. These results suggest that the effects of dietary SJ on alterations in mineral metabolism are not due to changes in GIT mineral elimination. In addition, it appears that the resistance of rabbits to dietary SJ intoxication is not caused by low GIT absorption of PA, but rather by efficient urinary elimination.