Calcium restriction and parathyroid hormone enhance renal compensatory growth

Calcium has been shown to control the proliferation of various cells in vitro and in vivo. Despite this information it is not known whether the Ca status or Ca-regulating hormones could modulate the degree of compensatory growth of the remaining kidney after renal mass reduction. In the present work the influence of dietary Ca, parathyroid hormone (PTH), and calcitonin (CT) on renal compensatory growth ( RCG ) was studied in unilaterally nephrectomized (UNI-NX) rats. UNI-NX rats were pair-fed diets with high (1.1%, HCa) or low (0.1% LCa) Ca content for 3, 8, and 15 days. After UNI-NX the wet weight of the remaining kidney increased much more in rats fed LCa than HCa. Values of dry weight, total protein, and DNA content were also significantly higher in the remaining kidney removed from rats fed LCa than from those fed HCa. LCa did not display such effects in sham-operated rats with intact renal mass. The amount of dietary Ca did not influence the progressive rise in glomerular filtration rate (clearance of inulin) of the remaining kidney as assessed 3, 8, and 15 days after UNI-NX. In UNI-NX rats fed LCa chronic administration of CT in doses that induced hypocalcemia did not inhibit the enhanced RCG induced by LCa. In UNI-NX rats fed HCa chronic administration of PTH mimicked the effect of LCa. In conclusion, dietary Ca restriction can markedly enhance the compensatory but not the normal growth of the kidney.(ABSTRACT TRUNCATED AT 250 WORDS)