Phosphate homeostasis has been considered until now a process mainly controlled by the SLC34 family of sodium dependent contransporters (NaPis) expressed in the intestine and in the kidney. Recently it has been shown that yet another family of transporters, the SLC20 family members Pit-1 and -2, may be involved in the regulation of phosphate homeostasis.

Since PTH is one of the main hormonal regulators of renal phosphate handling, we aimed to study the effect of a short-term application of PTH on the regulation of NaPi-IIc and Pit-2 in rat kidney. Rats were divided in four groups (control 30 minutes, PTH treated 30 minutes, control 60 minutes, PTH treated 60 minutes) and we measured Na-dependent phosphate uptake in the absence and presence of the type II specific transport inhibitor PFA, localization, and mRNA and protein expression of NaPi-IIa, NaPi-IIc, and Pit-2. Immunohistochemistry data show no apparent change in the localization of the NaPi-IIc and Pit2 transporter at both time points. PTH reduced total Na-dependent phosphate transport activity but had only little effect on the PFA-resistant activity. Real time PCR results show that 1h PTH did not alter the amount of NaPi-IIc and Pit-2 mRNA. Western blotting on renal brush border membranes showed similar results.

In conclusion, PTH reduces renal phosphate reabsorption by inducing internalization of NaPi-IIa but has no effects on NaPi-IIc and Pit-2.