Influence of metal ions on ruminal enzyme activities

Abstract

In vitro incubation experiments were conducted to evaluate the influence of several metal ions on urease, alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyltransferase (GGT) and glutamate dehydrogenase (GDH) enzyme activities of rumen fluid. Rumen fluid was collected from eight fistulated ewes and strained through a cheesecloth. Magnesium, copper and cadmium were each added to 10 ml of rumen fluid to obtain final concentrations of 5 mmol·l-1. After the addition of each metal ion, the mixture was shaken and incubated for 30 min at 37°C prior to enzyme activity assay in the rumen fluid with or without metal ions using spectrophotometric methods. Cadmium was found to inhibit urease, GDH, and GGT activity but on the other hand, it stimulated ALT and AST activity. Copper inhibited both GDH and urease activity with no significant differences for ALT, AST and GGT. Magnesium had stimulatory effect on activity of GGT and GDH. The results of this experiment indicate that metal ions copper, cadmium, and magnesium each affect some ruminal enzyme activity which play an important role in metabolism of nitrogenous substances and may further alter the nitrogen metabolism in the rumen of sheep.