Expression of 60-kDa and inducible 70-kDa stress proteins in gentamicin-induced acute renal failure

Chronic ingestion of high dosed Phikud Navakot extraction induces mesangiolysis in rats with alteration of AQP1 and Hsp60 expressions

Phikud Navakot (PN) is commonly used in Thai traditional medicine for alleviation of cardiovascular and cerebrovascular symptoms; however little is known about the chronic toxicity effects of the extracts from the herbs in PN. Repeated extraction doses of 10, 100, and 1,000 mg/kg/day were randomly administered to both male and female Sprague Dawley rats for 12 months. Histopathological study revealed that mesangiolysis was predominately found at the highest dose. Aquaporin 1 (AQP1) expression in the mesangiolytic glomeruli was significantly lower than in the intact glomeruli. This may be relevant to an imbalance of vascular function manifested by AQP1 alteration. In the mesangiolytic glomeruli, 60 kDa heat shock protein (Hsp60) was significantly upregulated on the endothelial lining cells of aneurysm and vascular cyst. Hsp60 increase may be related to endothelial cell damage due to its intracellular protective role. Blood urea nitrogen and creatinine levels remained within their normal range indicating well-functioning renal reserve function. In conclusion, high dosed PN may affect the endothelium leading to inability of vascular permeability and consequence to mesangiolysis. Our results suggest that only a high dose of chronic oral administration of PN is relatively toxic in association with mesangiolysis. The NOAEL was determined to be 100 mg/kg/day.

Expression of pI(Cln) in Escherichia coli gives a strong tolerance to hypotonic stress

We amplified the coding region DNA sequence from a rat renal pI(Cln) cDNA by PCR and expressed the protein in Escherichia coli cells. The cells were exposed to hypotonic conditions followed by spreading them onto LB plates for subsequent colony survival assay. The present study demonstrated that the cells expressing pI(Cln) exhibit a strong resistance to hypotonic stress. Moreover, the resistance was specifically inhibited by extracellular ATP and some anion channel inhibitors. These findings indicate that the expression of pI(Cln) directly confers tolerance to hypotonic stress, and pI(Cln) is concluded to be an important molecule for cell-volume regulation.

pICln predominantly localizes at luminal surface membranes of distal tubules and Henle's ascending limbs

We produced a highly specific antibody to the C-terminal peptide sequence of pICln. It recognized pICln with a 38-kDa molecular mass on SDS-polyacrylamide gel electrophoresis, coinciding with that previously reported. During native polyacrylamide gel electrophoresis, three immunoreactive bands (38, 70, and 130 kDa) were detected. The isoelectric point of pICln was calculated to be 4.0. Subcellular localization study showed the presence of pICln in the soluble and microsomal fraction. pICln can be easily solubilized from the membrane fraction with Triton X-100. From immunohistochemical observations, we found pICln to be obviously located on the luminal surface membranes of the distal tubules and Henle's loop ascending limbs, and it can also be found inside proximal tubular cells. The present results suggested that pICln functions as a "cytosolic anchor = membrane insertion" model, and it plays important roles in the "urine dilution segment" cells of nephrons.