ACUTE EFFECTS OF SOFT DRINK INTAKE ON CALCIUM AND PHOSPHATE-METABOLISM IN IMMATURE AND ADULT RATS

Objective: To test the acute effects of the intake of a phosphoric aci d containing soft drink on acid- base balance and on calcium and phosp hate metabolism. Material and methods. We studied 14 young adult male Sprague-Dawley rats aged 90 days, and 14 immature animals aged 30 days . Half of the animals in each group were randomly assigned to receive either tap water (controls), or Coca-Cola ad libitum for seven days. A fter this period, the rats were individually placed in metabolic cages to collect 24 hours urine, and they were exsanguinated by aortic punc ture. Immediately, pH and ionized calcium were measured in whole blood . Creatinine, phosphate and total calcium were determined in the urine and plasma. Plasma levels of PTH, 1 alpha, 25 (OH)(2) D-3 and 25 OH D -3 were measured by IRMA and RIA commercial kits. Results. The animals receiving the soft drink, both adults and immature, developed signifi cant hypercalciuria and hyperphosphaturia. In immature animals, the pl asma pH dropped from 7.45 +/- 0.04 to 7.33 +/- 0.02 (p < 0.05) but did not change in adult animals. Ionized calcium dropped significantly fr om 1.06 +/- 0.04 to 0.80 +/- 0.06 meq/L (p < 0.05) in immature animals but not in the adult animals. Only immature rats developed significan t reduction of 1 alpha, 25 (OH)(2) D3 and 25 OH D-3, whereas only the adult rats developed significant hyperparathyroidism. Immature animals showed more severe derangement of calcium and phosphate metabolism re lated to soft drink intake.