Renal abnormality of calcium handling in spontaneously hypertensive rats.

Hypercalciuria has been observed in human and experimental hypertension. The distal convoluted tubule (DCT) is the site of fine regulation for Ca2+ excretion. We assessed the cellular factors responsible for Ca2+ reabsorption in the DCT of spontaneously hypertensive rats (SHR). Vitamin D3 dependent Ca-binding protein 28k (CaBP28k), a factor involved in Ca2+ influx, and plasma membrane Ca ATPases (PMCA), a factor involved in Ca2+ efflux, were studied in hypertensive 16-week-old SHR and normotensive Wistar-Kyoto rats (WKY). mRNA levels for CaBP28k, PMCA 2 and PMCA 4 were not different in the two strains. However, CaBP28k protein was more abundant, and PMCA protein was less abundant in SHR than in WKY. PMCA antibody recognized only DCT in the two strains. In conclusion, decreased PMCA in DCT may be responsible for the hypercalciuria in SHR.