ORAL CALCIUM-CARBONATE ADMINISTRATION AMELIORATES THE PROGRESSION OF RENAL-FAILURE IN RATS WITH HYPERTENSION

Oral calcium supplementation is reported to have phosphate-binding and antihypertensive effects, Since both phosphate binders and antihypert ensive agents are reported to attenuate renal injury, we studied the e ffect of oral calcium carbonate (CaCO3) administration on the course o f renal deterioration using doxorubicin-induced renal failure in rats treated with deoxycorticosterone acetate and salt for 10 weeks. Rats w ere divided into four groups: the CaCO3 (6.0 g/kg/d) group (n = 12), t he aluminum hydroxide (Al(OH)(3); 6.0 g/kg/d) group (n = 11, as a phos phate-binder control), the hydralazine (10 mg/kg/d) group (n = 11, as an antihypertensive control), and the control group (n = 12). All agen ts were given as a mixed chow diet, Blood pressure and urinary protein excretion progressively increased in the control rats. CaCO3 and hydr alazine lowered blood pressure, but Al(OH)(3) did not (185 +/- 4 mm Hg , control; 160 +/- 5 mm Hg, CaCO3; 171 +/- 8 mm Hg, Al(OH)(3); 156 +/- 5 mm Hg, hydralazine at week 10). Proteinuria was reduced in the rats treated with CaCO3 and Al(OH)(3) compared with those without the trea tment (986 +/- 86 mg/d, control; 551 +/- 54 mg/d, CaCO3; 527 +/- 31 mg /d, Al(OH)(3); and 955 +/- 68 mg/d, hydralazine at week 10). Serum pho sphate concentration and calcium phosphate products also were signific antly lower in both the CaCO3 and Al(OH)(3) groups than in the control group. At week 10, increased serum urea nitrogen, impaired renal func tion, and glomerular sclerosis present in the control group were signi ficantly attenuated in both in the CaCO3 and Al(OH)(3) groups. No sign ificant attenuation was observed in the hydralazine group in spite of lower blood pressure. We conclude that oral CaCO3 administration atten uates the progression of renal failure associated with hypertension. T his effect appears to be primarily related to its effects on divalent mineral metabolism and not on blood pressure. (C) 1935 by the National Kidney Foundation, Inc.