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In most mammalian species, serum amyloid A isoform 3 (SAA3) appears to be the predominant SAA isoform expressed extrahepatically. However, human SAA3 gene expression has not been detected previously and, therefore, this gene was referred to as a pseudogene. We report for the first time the transcriptional expression of human SAA3. Human SAA3 gene expression was detected by RT-PCR after stimulation of mammary gland epithelial cells with either prolactin (PRL) or lipopolysaccharide (LPS). The full-length 655bp cDNA sequence for this mammary-associated serum amyloid A3 (M-SAA3) was obtained using 5' and 3' rapid amplification of cDNA ends (RACE). The human M-SAA3 transcript would conceptually translate into a 42 residue mature protein, which is smaller than other mammalian SAA3 isoforms that are typically 104-113 amino acids in length. This study defines the cDNA sequence for human SAA3 and also demonstrates the upregulation of M-SAA3 expression in response to the lactational hormone PRL or to an acute phase stimulant such as LPS.

We previously determined that the N-terminal region of bovine mammary-associated serum amyloid A3 (M-SAA3) increased intestinal mucin MUC3 levels in HT29 human intestinal cells by approximately 2.5-fold, relative to untreated cells. This study shows that the human M-SAA3 N-terminal peptide further enhances MUC3 transcript levels by approximately 4.3-fold in these cells (p

Glutathione (GSH)-dependent reactions are an important cellular defense against ischemic or oxidative injury, although their role in toxin-induced renal cellular injury is less clear. Because of the known sulfhydryl reactivity of mercury (M), we hypothesized that GSH could modify mercuric chloride (MC)-induced acute renal failure (ARF). Therefore, we evaluated the effects of glutathione monoethyl ester (GE), which produces high intrarenal levels of GSH, on the nephrotoxicity of MC. GE treatment in normal rats did not alter their creatinine clearance (CCr), fractional sodium (CNa/CCr) or lysozyme (CLy/CCr) excretion, but histologically resulted in prominent proximal tubular vacuolization. GE pretreatment in rats with MC-induced ARF resulted in partial preservation of their CCr, CNa/CCr and CLy/CCr. Renal histology also demonstrated a reduction in tubular necrosis. M content in the renal cortex 3 following MC was lower in the MC + GE group, but levels were higher in the liver and inner stripe/inner medulla as compared to animals receiving MC alone. No differences were seen in the outer stripe at 3 h or in any of the tissues 24 h following MC injection. Thus, GE moderated MC-induced ARF, likely by providing a large intracellular sulfhydryl pool and thereby reducing M reactivity with endogenous cellular proteins and enzymes.

Dimethylthiourea (DMTU), a free radical scavenger, was administered to rats to study its effect on renal and hepatic glutathione metabolism, since it is a potential sulfhydryl donor. Six hours following DMTU, renal GSH content was significantly (P < 0.05) increased (10%), and was increased further after 24 h (28%) (P < 0.001). Hepatic GSH content was also significantly (P < 0.001) elevated at 6 and 24 h (5 and 33%, respectively). Seven days of daily DMTU therapy significantly (P < 0.001) increased renal and hepatic GSH content by 36 and 54%, respectively, which was associated with a significant (P < 0.001) increase in the renal activities of glutathione peroxidase (GP) by 38%, glutathione transferase (GT) by 92%, and glutathione reductase (GR) by 19% (P < 0.05). Significantly increased activities of hepatic GP by 84% (P < 0.01) and GT by 101% (P < 0.001) also occurred in DMTU-treated rats after 7 days of continuous therapy. From these data, we conclude that DMTU stimulates renal and hepatic GSH metabolism, which may be important in mediating DMTU's protective effect against free radical-induced tissue injury.

Glutathione (GSH) metabolism, a tissue detoxification pathway, was evaluated in rats with adriamycin nephrosis (AN) treated with dimethylthiourea (DMTU), a free radical scavenger. After 7 days of DMTU, a significant reduction in proteinuria occurred as compared to AN controls (62.4 +/- 13.3 vs. 155.0 +/- 24.0 mg/24 h). A significant increase in renal cortical GSH content as well as glutathione peroxidase (GP) and transferase (GT) activities occurred in DMTU-treated rats as compared to controls. Glutathione monoethyl ester (GME) administration alone reduced proteinuria by 21% in AN, which was not significant despite a large increase in the renal GSH content, however, GP and GT activities were not increased by GME. We conclude that DMTU ameliorates glomerular injury in AN by stimulating GSH metabolism.