Abstract
Summary
Utilizing ureteral occlusion during low urine flow and the stop-flow technique during mannitol diureses it was noted that the calcium specific activity in the urine fractions obtained upon release of the ureteral clamp was altered in a manner which could be predicted from the state of kidney tissue calcium. It was concluded that the prolonged contact of the luminal fluid with the tubular epithelium when caused by a decrease in glomerular filtration rate resulting either from administration of massive doses of adrenergic drugs or from mechanical obstruction of urine flow, had provided time for a discernible addition of calcium from the epithelial cells to the tubular urine. Calcium concentrations in the stop-flow samples showed that addition of cellular calcium to the luminal fluid did not imply an active or net secretion.
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