HYPERCALCIURIC RESPONSE TO DIETARY SUPPLEMENTATION WITH DL-METHIONINEAND AMMONIUM-SULFATE

Renal Ca and inorganic P (P(i)) excretion were evaluated in Single Com b White Leghorn pullets reared on diets containing 1 or 3.5% Ca alone or supplemented with.6% DL-methionine or .53% ammonium sulfate. Plasma and urine samples were collected during a CONTROL period, and while 2 00 mM Ca was infused intravenously (Ca-LOADING). Excess Ca, whether su pplied chronically in the feed or infused acutely into birds fed 1% Ca diets, significantly reduced glomerular filtration rates, effective r enal plasma flow rates, and P(i) excretion rates and significantly inc reased Ca excretion rates and urine pH. Birds fed diets supplemented w ith DL-methionine and ammonium sulfate maintained significantly lower plasma Ca concentrations during the CONTROL and Ca-LOADING periods tha n birds fed the respective 1 or 3.5% Ca basal diets. When compared wit h birds fed the respective 1 or 3.5% Ca basal diets, birds fed the 1% Ca diet supplemented with ammonium sulfate or the 3.5% Ca diet supplem ented with DL-methionine had significantly higher absolute urinary Ca excretion rates during Ca-LOADING. Fractional Ca excretion during Ca-L OADING was significantly higher in birds fed 3.5% Ca supplemented with DL-methionine or ammonium sulfate than in birds fed the 3.5% Ca basal diet. These results indicate that DL-methionine and ammonium sulfate accelerated urinary Ca excretion and reduced Ca retention in the extra cellular fluid. The hypercalciuric efficacies of DL-methionine and amm onium sulfate were revealed only when the filtered load of Ca was incr eased through intravenous Ca infusions.