Phosphaturia of Aging: Studies on Mechanisms
Corvilain and Abramaw (1) reported a lower serum inorganic phosphorus level associated with a reduction in maximum tubular reabsorption of phosphate TmP) in adults when compared to children in active growth. Insogna and associates (2) also noted a reduction in serum phosphorus level and renal TmP in the elderly when compared to younger adult subjects. In addition, these investigators observed increases in immunoassayable parathyroid hormone (PTH) level in the blood and cyclic AMP (cAMP) excretion in the urine of the elderly subjects. Based on the observations that intestinal calcium absorption is reduced in elderly subjects (3,4) these authors suggested that the increased PTH was secondary to the suboptimal enteral calcium absorption and that this hyperparathyroidism in turn led to “renal phosphate wasting” and hypophosphatemia in the elderly. Berlyne and coworkers (5) confirmed the observation of an increase in PTH secretion and a decrease in TmP, as well as a reduction in glanerular filtration rate, in the elderly. They postulated that the hyperparathyroidism may, in addition, caused an increase in calcium mobilization from the skeleton and thus contributed towards the development of senile osteoporosis.
KeywordsBrush Border Membrane Vesicle Intestinal Calcium Absorption Renal Response Renal Phosphate Serum Phosphorus Level
Unable to display preview. Download preview PDF.
- 3.J. C. Gallagher, B. L. Riggs, C. M. Jerpbak and C.D. Arnaud: The effect of age on serum inmunoreactive parathyroid hormone in normal and osteoporotic woman. J Lab Clin Med 95: 373–384, 1981.Google Scholar
- 4.J. R. Bullamore, R. Wilkinson, J.C. Gallagher, B.E.C. Nordin and D. H. Marshall: Effects of age on calcium absorption. Lancet II: 535–537, 1970. 2–4.Google Scholar
- 5.G.M. Berlyne, J. Ben-Ari, A. Kushelevsky, A. Idelman, D. Galinsky, M. Hirsch, R. Schainkin, R. Yagil and M. Zlotnik: The etiology of senile osteoporosis: secondary hyperparathyroidism due to renal failure. Quart J Med 175: 505–521, 1975.Google Scholar
- 9.C. Evers, H. Murer and R. Kinne: Effect of parathyrin on the transport properties of isolated brush-border vesicles. Biochem J 172: 46–56, 1978.Google Scholar
- 11.K.A. Hruska, S.C. Mills, S. Khalifa and M.R. Hammerman: Phosphorylation of renal brush-border membrane vesicles. Effect of calcium uptake and membrane content of polyphosphoinositides. J Biological Chem 258: 2501–2507, 1983.Google Scholar