Urine Ca excretion (mean ± SE) in the control (Ctl) and genetic hypercalciuric stone-forming (GHS) rats after 2, 4, and 6 wk of consuming 15 g/d of a high Ca diet (1.2% Ca, HCD) or a low Ca diet (0.02% Ca, LCD). The 24-h urines were collected in concentrated HCl and urine Ca was measured photometrically. aDifferent from Ctl eating HCD, p < 0.05; bdifferent from GHS eating HCD, p < 0.05; cdifferent from Ctl eating LCD, p < 0.05.