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Expression and role of parathyroid hormone-related protein in human renal proximal tubule cells during recovery from ATP depletion. J Am Soc Nephrol 1999 Feb;10(2):238-44

Date

04/24/1999

Pubmed ID

10215322

DOI

10.1681/ASN.V102238

Scopus ID

2-s2.0-0345683509   18 Citations

Abstract

Parathyroid hormone (PTH)-related protein (PTHrP) is widely expressed in normal fetal and adult tissues and regulates growth and differentiation in a number of organ systems. Although various renal cell types produce PTHrP, and PTHrP expression in rat proximal renal tubules is upregulated in response to ischemic injury in vivo, the role of PTHrP in the kidney is unknown. To study the effects of injury on PTHrP expression and its consequences in more detail, the immortalized human proximal tubule cell line HK-2 was used in an in vitro model of ATP depletion to mimic in vivo renal ischemic injury. These cells secrete PTHrP into conditioned medium and express the type I PTH/PTHrP receptor. Treatment of confluent HK-2 cells for 2 h with substrate-free, glucose-free medium containing the mitochondrial inhibitor antimycin A (1 microM) resulted in 75% depletion of cellular ATP. After an additional 2 h in glucose-containing medium, cellular ATP levels recovered to approximately 75% of baseline levels. PTHrP mRNA levels, as measured in RNase protection assays, peaked at 2 h into the recovery period (at four times baseline expression). The increase in PTHrP mRNA expression was correlated with an increase in PTHrP protein content in HK-2 cells at 2 to 6 h into the recovery period. Heat shock protein-70 mRNA expression was not detectable under baseline conditions but likewise peaked at 2 h into the recovery period. Treatment of HK-2 cells during the recovery period after injury with an anti-PTHrP(1-36) antibody (at a dilution of 1:250) resulted in significant reductions in cell number and uptake of [3H]thymidine, compared with nonimmune serum at the same titer. Similar results were observed in uninjured HK-2 cells. It is concluded that this in vitro model of ATP depletion in a human proximal tubule cell line reproduces the pattern of gene expression previously observed in vivo in rat kidney after ischemic injury and that PTHrP plays a mitogenic role in the proliferative response after energy depletion.

Author List

García-Ocaña A, Galbraith SC, Van Why SK, Yang K, Golovyan L, Dann P, Zager RA, Stewart AF, Siegel NJ, Orloff JJ

Author

Scott K. Van Why MD Professor in the Pediatrics department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Adenosine Diphosphate
Cell Division
Cell Line
DNA
Gene Expression
Humans
Kidney Tubules, Proximal
Parathyroid Hormone-Related Protein
Protein Biosynthesis
Proteins