*Faculty of veterinary medicine, Kosice, Slovak Republic

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 37oC for 30 min. Two different concentrations of salts of divalent ions were tested (5 and 20 x10-3 mol/L). The higher concentration of Cu2+ and Zn2+ produced a higher inhibitory effect (from 50 to 70 % of control ALT and AST activity) by Cu2+ and Zn2+. The lower assayed concentration of Cu2+ produced 57% inhibition of GDH activity. Salts of divalent ions such as Ba2+, Cu2+, Cd2+, Zn2+ and Mg2+ resulted in the activation of GDH from 216 to 297 % of total GDH activity, when assayed at a relative concentration of 20 x 10-3 mol/L. The lower concentration of Ca2+ and Zn2+ iduced activation of ALT from 146 to 186%, while Cd2+, Zn2+ and Ca2+ 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. Key words: divalent ion, enzyme activation, enzyme inhibition, ruminal enzyme, shee