The subcellular distribution of gold in monkey liver, kidney and spleen, in vivo

Gold induced nephropathy in rheumatoid arthritis and HLA class II genes

OBJECTIVES

To elucidate the role of HLA-DRB, -DQA, and -DQB genes in patients with rheumatoid arthritis (RA) who developed gold induced nephropathy.

METHODS

Southern blot analysis of HLA-DRB, -DQA, and -DQB genes was performed on DNA from 27 patients with RA with gold induced nephropathy, 37 patients with RA who were treated with gold but did not develop nephropathy, and 122 ethnically matched normal subjects.

RESULTS

The 4.7 kb DQA1/Taq I band associated with DQA1*0501 and DR3 and DR5 was found in 16 (59%) patients with gold induced nephropathy compared with five (14%) patients without gold induced nephropathy.

CONCLUSION

It is concluded that HLA-DQA region genes may be an important susceptibility factor for the development of gold induced nephropathy in patients with RA.

Triethylphosphine gold: cellular uptake and disposition after single and repeated oral doses in rats

The tissue and subcellular pharmacokinetics of gold following single and repeated oral doses of triethylphosphine gold (auranofin) has been studied in rats. After a single dose, the tissue and subcellular gold levels were 5-10 times lower than those reached with injectable gold compounds. In the liver tissues, gold concentrations peaked within 24 h followed by a biphasic clearance, with an initial rapid phase (t1/2 32 h) and a slow terminal phase (t 1/2 11 days). Renal gold concentrations continued to increase for 3 to 5 days and then decreased exponentially with a first order t 1/2 of about 7 days. Intracellularly, between 60-80% of hepatic and 50-70% of renal gold was present in the cytosol. In rats given repeated doses of auranofin, the hepatic and renal gold concentrations were 3-5 times higher than those measured after a single dose. The proportion of cellular gold present in the cytosol was markedly lower, with 43% in the liver and 30% in kidney tissues. In both the liver and kidney, gold concentrations were dose-dependent, whereas in the gastrointestinal tissues the increases as a function of dose were minimal.

Role of metallothionein in cellular uptake and disposition of gold sodium thiomalate

Rat liver and kidney tissue uptake of gold and its localization in the cytosol was studied following various doses of gold sodium thiomalate (GST). The timecourse of gold incorporation into intracellular gold-binding ligands following repeated injections of GST was also investigated (11 injections, one dose/week). Results show that between 30 and 60% of the hepatic and renal gold was localized in the cytosol over a wide range of GST doses. This was also true following repeated doses. In the kidney, the binding of gold to high molecular weight (HMW) proteins was saturated after the third GST dose, while incorporation into the metallothioneins (MT) continued to increase, accounting for as much as 50% of cytosolic gold. On the other hand the binding to hepatic MT was about 10x lower, and the proportion of cytosolic gold incorporated into the MT, decreased from 30% (after first 3 GST injections) to about 15% (following the last 3 injections). The results show that the stimulation of MT biosynthesis in different tissues as a response to the injected GST is not the same and varies within each organ with the dose and/or the duration of repeated exposure. In the liver, the ability of gold to induce MT synthesis was limited and the importance of MT in the cellular uptake and disposition of gold may largely be confined to the kidneys. It is suggested that besides playing a possible role in the detoxification of cellular gold, particularly in the kidney, MT may also contribute towards the retention and localization of gold in the tissues.

cis-Platinum: subcellular distribution and binding to cytosolic ligands

In the present experiments the tissue uptake and subcellular distribution of Pt were measured in the liver and kidney of rats injected intraperitonially with 5 mg cis-diamminedichloroplatinum (cis-DPP)/kg. The binding of Pt to cytosolic ligands was also investigated. In both the liver and kidney Pt concentration was maximal within 24 hr following cis-DDP injection. Thereafter the clearance was bimodal with a rapid phase of about 48 hr (with 60-70% clearance) followed by a slow incomplete phase. In the kidney relatively high concentrations of Pt were measured in the microsomal, lysosomal and mitochondrial fractions. But in the liver the higher levels were found in the microsomal and nuclear fractions. On average 62% (kidney) and 89% (liver) of the cellular Pt were localized in the cytosol. At 24 hr following cis-DDP injection, about 52% of cytosolic Pt was present as low molecular weight species (molecular weight less than 1000) and the remainder as protein-bound. About 25% was bound to a metallothionein-like protein in the liver as well as the kidneys. It is suggested that the high localization of cellular Pt in the cytosol and the presence of a high proportion as non-protein bound species may be important factors in relation to the therapeutic as well as the toxic effects of cis-DDP.

The effect of zinc and copper pretreatment on the binding of gold (I) to hepatic and renal metallothioneins

In the first part of this study, single s.c. injections of gold (I) sodium thiomalate were given to male Wistar rats at various dose levels and sacrificed either at 48 hr or 4 days later. The results indicate that though metallothioneins play a significant role in the sequestration of renal gold, the ability of gold itself to induce synthesis of the metalloprotein was limited in the kidneys and practically insignificant in the liver. Pre-injection with zinc however, (4 mg/kg body wt), significantly (P less than 0.01) enhanced the uptake of gold into the metallothioneins both, in the liver as well as the kidneys. The pretreatment increased the proportion of cytosolic gold incorporated into the thioneins from 29% to 48% in the kidneys and from 22% to 47% in the liver. Concurrent increases in the uptake of zinc and copper into the thioneins was also observed. Pre-injection with copper induced a similar effect in the kidneys only. There was no significant difference in the overall uptake of gold into the cytosol itself between the control animals (injected with gold only) and those pretreated with either zinc or copper. This indicated that the increased uptake of gold into the thioneins in the pretreated animals were due to enhanced synthesis of metallothioneins and subsequent increased binding of gold to thioneins rather than increased levels of intracellular gold itself. It is suggested that increased protection against the deposition and possible toxicity of gold in the cell organelles of the liver and kidney tissues may be provided by an increased binding of gold to metallothioneins through pretreatment with zinc, and to a lesser extent copper.

Comparative studies on the distribution of gold, copper and zinc in the livers and kidneys of rats and hamsters after treatment with sodium [195Au]-aurothiomalate

The distribution of gold, copper and zinc in the livers and kidneys of female rats and hamsters was determined after intraperitoneal injection of sodium [195Au]-aurothiomalate. After five doses of sodium [195Au]-aurothiomalate (1 mg Au(I) per kg body weight), the hepatic and renal concentrations of Au were greater in rats than in hamsters. In the former species, treatment with the Au(I)-compound led to an increase in the Cu-concentration of the kidney and to the synthesis of a (Cu, Au)-metallothionein. In either species binding of Au to the hepatic metallothionein was insignificant. The renal (Cu, Au)-metallothionein from the sodium [195Au]-aurothiomalate-treated rat appeared to be extremely heterogeneous and was resolved into at least four components on ion exchange chromatography.

Effects of gold sodium thiomalate on cytosolic copper and zinc in the rat kidney and liver tissues

1. Male Wistar rats were given a single subcutaneous injection of gold sodium thiomalate and killed 7 days later. The binding of Au, Zn and Cu to the kidney and liver cytosolic proteins of control and gold-treated rats and determined. 2. In the renal cytosol of Au(I)- exposed rats, the binding of Cu to the low-molecular-weight (LMW) proteins increased by 62%, and to the high-molecular-weight (HMW) proteins the binding decreased by 54%. The incorporation of Cu into the liver cytosolic proteins increased, in both, the HMW and the LMW proteins. The binding of Zn into the renal cytosolic proteins was increased by 39% (HMW proteins) and 100% (LMW proteins). Au(I) had little effect on the binding of Zn to the cytosolic proteins in the liver. 3. It is suggested that the therapeutic action of gold complexes may be mediated, to some extent, by its effects on the metabolism of Cu and/or Zn.