INTRODUCTION
Copper and nickel metal ions play important roles in
biological systems. Copper plays a key role during cell
respiration in the blood of invertebrate animals and in the
formation of hemocyanin and plays a definitive role in the
intrinsic mechanisms regulating vital biological processes (1).
Copper is involved in hemopiesis and in the maintenance of
vascular and skeletal integrity in addition to the structure and
function of the central nervous system. A variety of clinical
disorders such as anemia, depression of growth, impaired
reproductive performance, heart failure, and gastrointestinal
disturbances have been associated with a dietary deficiency of
copper (2). Overexposure to copper causes a metallic taste,
nausea, vomiting, epigastrial burning, diarrhea, heptatic neurosis,
gastrointestinal bleeding, hemoglobinuria, hypertension, and
convulsions. Nickel is an essential metal for plants and animals
and has biological importance (3). Urease, which is a biologi
cally important enzyme, is a nickel enzyme (4). As compared