Supported in part by grants from the Ministry of Science and Technology (PB98-0700-C02-01/02 and SAF 2002-04356-C01/03), Comunidad Autónoma de Madrid (CAM 08.6/0038.2000 1/ 2) and the Spanish Society of Nephrology.
Parathyroid hormone-related protein (PTHrP) is present in the kidney, where it modulates glomerular function, and also has mitogenic effects. Both PTH and PTHrP bind to the common PTH/PTHrP type 1 receptor (PTH1R). We have recently found a renal PTHrP upregulation in streptozotozin-induced diabetic nephropathy. In the present study, we analyzed the effect of high glucose (450 mg/dl) and/or insulin (10 mg/ ml) on the expression of PTHrP and the PTH1R in mouse mesangial cells (MMC) and in mice tubular cells (MTC).
MCT cells were grown in RPMI 1640 with 10% fetal bovine serum (FBS), and antibiotics; while MMC (ATCC number CRL-1927) were cultured in a 3:1 mixture of DMEM and Ham`s F12 medium with 5% FBS, in 5% CO2 at 37°C. The expression of both PTHrP and the PTH1R, at mRNA and protein levels, were determined by RT-PCR and/or RNAse protection assay and Western blot, respectively.
In the presence of high glucose medium, an upregulation of PTHrP -3-fold over control (mRNA and protein)-was found in both MMC and MCT. In MCT cells, but not in MMC, insulin treatment prevented this PTHrP overexpression. Moreover, in the presence of high glucose medium, an upregulation of the PTH1R -3-fold over control (mRNA and protein) - was found in both MCT and MMC, and it was unaffected by insulin treatment.
Conclusions: These findings indicate that PTHrP/PTH1R expression can be modulated by high glucose and/or insulin in glomerular and tubular cells in culture. Much work needs to be done in order to understand the pathophysiological significance of this effect of high glucose and insulin. However, taken together with our recent in vivo studies, these findings suggest a role of PTHrP on the renal changes associated with diabetes.
