Subcellular distribution of copper in the kidneys of normal, copper-poisoned, and thiomolybdate-treated sheep

Abstract

Twenty-seven sheep given either copper (Cu) and/or tetrathiomolybdate (TM) were used to study the subcellular distribution of Cu within the kidney and to monitor the location of lysosomes within the subcellular fractions using acid phosphatase (AP) as a marker enzyme. Copper dosing alone increased the Cu content in the liver and the kidneys. The administration of intravenous TM prevented the development of chronic copper poisoning (CCP) in sheep, reduced the rate of accumulation of Cu in the liver of Cu-dosed animals, but increased the Cu content of kidneys in both the control and Cu-dosed sheep. The total amount of Cu that accumulated in the kidneys of sheep given TM appears to depend on several factors: a) liver Cu concentration, b) Cu intake, and c) dosage of TM. Thus, the highest Cu concentration was found in the kidneys of sheep that continued to receive Cu orally at the same time as they were given TM. The intracellular distribution of Cu and AP in thfe kidneys showed that in the control sheep given neither Cu or TM, the highest proportion of Cu was in the cytosol fraction, and the highest specific activity of AP was in the light mitochondrial (lysosomal) fraction. Dosing with Cu markedly increased the Cu concentration and greatly elevated the total activity of AP in the heavier fractions, i.e., the nuclear (N) and heavy mitochondrial (MH). Thus, the increase in Cu observed in the N and MH fractions was not caused by an accumulation of Cu by nuclei and mitochondria, but was due to an accumulation of Cu by lysosomes that sedimented with the heavier fractions. The intracellular distribution of Cu in the kidneys of TM-treated sheep was similar to that seen in Cu-loaded sheep. Although Cu accumulated readily in the kidneys of animals receiving TM, kidney function tests showed neither glomerular nor tubular functional impairment.