Effect of divalent ions on ruminal enzyme activities in sheep

Abstract

The effect of different salts of divalent ions as potential inhibitors and stimulators of ruminal alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyltransferase (GGT) and glutamate dehydrogenase (GDH) activities in sheep was assessed using biochemical assays. Ruminal fluid was obtained from six cannulated ewes. Effects of ZnCl2, CuCl2, MgCl2, BaCl2 and CoCl2 on ruminal enzyme activities were tested after incubation of ruminal fluid in the presence of the salts at 37 o C for 30 min. Two different concentrations of salts of divalent ions were tested (5 and 20 x10 -3 mol/L). The higher concentration of Cu 2+ and Zn 2+ produced a higher inhibitory effect (from 50 to 70% of control ALT and AST activity) by Cu 2+ and Zn 2+ . The lower assayed concentration of Cu 2+ produced 57% inhibition of GDH activity. Salts of divalent ions such as Ba 2+ ,C u 2+ , Cd 2+ ,Z n 2+ and Mg 2+ resulted in the activation of GDH from 216 to 297% of total GDH activity, when assayed at a relative concentration of 20 x1 0 -3 mol/L. The lower concentration of Ca 2+ and Zn 2+ iduced activation of ALT from 146 to 186%, while Cd 2+ ,Z n 2+ and Ca 2+ resulted in the activation of AST ranging from 127 to 172%. The results of the study indicate that the effect of divalent ions on ruminal enzyme activities depend on their relative concentration and which enzyme is assayed.