An Evaluation of Possible Sites of Phosphate Secretion in the Rat Nephron
Although net secretion of phosphate has been demonstrated in non-mammalian species, the secretion of phosphate in mammals has been difficult to demonstrate using clearance methods (1). In these studies, plasma phosphate was elevated by infusion of phosphate and the clearance of phosphate was compared to the clearance of a glomerular marker (usually inulin). The results were equivocal with some investigators reporting net secretion, while others did not. In recent studies by Boudry et al (2), phosphate clearances were greater than inulin clearances in conscious rats when plasma Pi concentration was corrected for ultrafilterability. Likewise, in studies by Troehler et al (3), rats fed a high phosphate diet for 10 days and then infused acutely with phosphate, had a FEp% of 97% without correction for plasma ultrafilterability. Since it is highly unlikely that unidirectional outflux of phosphate (reabsorption) was abolished completely in these studies, this data has been taken as evidence for a secretory component of net phosphate transport if not net secretion per se.
KeywordsProximal Tubule Phosphate Transport Secretory Component Phosphate Reabsorption Single Nephron Glomerular Filtration Rate
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- 2.Boudry, J.F., Troehler, U., Toubai, M., Fleisch, H., and Bonjour, J.P.: Secretion of inorganic phosphate in the rat nephron. Clin. Sci. Mol. Med. 48: 475–489, 1975.Google Scholar
- 8.Schneider, E.G., and McLane, L.A.: Evidence for a peritubularto luminal flux of phosphate in the dog kidney. Am. J. Physiol. 1: 159–166, 1977.Google Scholar
- 9.Knox, F.G., Haas, J.A., Berndt, T., Marchand, G.R., Youngberg, S.P.: Phosphate transport in superficial and deep nephrons in phosphate loaded rats. Am. J. Physiol., in press, 1977.Google Scholar
- 10.Lang, F.C., Greger, R.F., Marchand, G.R., and Knox, F.G.: Stationary microperfusion study of phosphate reabsorption in proximal and distal nephron segments. Pflugers Archiv., in press, 1977.Google Scholar
- 11.Haas, J.A., Larson, M., Marchand, G.R., Lang, F., Greger, R., and Knox, F.G.: Phosphaturic effect of furosemide, role of PTH and carbonic anhydrase. Am. J. Physiol. 1: F105–110, 1977.Google Scholar