The Biochemical Indices of Experimental Phosphorus Depletion (PD): A Re-Examination of Their Physiological Implications
The biochemical features observed in experimental phosphorus (P) depletion include hypercalcemia (↑P-Ca), hypophosphatemia (↓P-P), hypercalciuria (↑U-Ca), hypophosphaturia (↓U-P) and intestinal calcium (Ca) hyperabsorption (1–7). Exogenous P deprivation is the usual mode of inducing PD and has been considered fundamental in the generation of the various biochemical changes (Figure 1). However, it is entirely reasonable to postulate that these changes also may be induced or aborted by modifying the metabolic need for P. In the present study we observed that normal young rats maintained on normal P diets may develop biochemical features of PD if they undergo unusual and spontaneous acceleration in growth. On the other hand, in young rats with growth arrest induced by hypophysectomy, both the biochemical and clinical changes caused by low P diet may either be aborted or attenuated. These findings stress the importance of defining the prevailing anabolic need of experimental animals in interpreting both the adequacy of dietary P and the significance of the clinical and the biochemical changes of PD. Some relevant examples will be discussed. We also provide evidence demonstrating that in young rats PD results in a net reduction in intestinal Ca retention. Since both the synthesis of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) and its accumulation in intestinal mucosa are increased in P deprived rats (8,9), this finding may represent an example in which the physiological interrelationship between the activity of 1,25(OH)2D3 and net intestinal Ca retention is dissociated.
KeywordsBiochemical Index Intestinal Calcium Transport Phosphorus Depletion Experimental Phosphorus Experimental Rickets
Unable to display preview. Download preview PDF.
- 1.Day HG, McCollum EV: Mineral metabolism, growth, symptomatology of rats on diet extremely deficient in phosphorus. J. Biol. Chem. 130: 269–283, 1939.Google Scholar
- 2.Freeman S, McLean FC: Experimental rickets. Blood and tissue changes in puppies receiving a diet very low in phosphorus with and without vitamin D. Arch. Path. 32: 387–408, 1941.Google Scholar
- 3.Aubel CE: The effects of low phosphorus rations on growing pigs. J. Agricultural Res. 52: 149–159, 1936.Google Scholar
- 14.Copp DH, Snider AP: Study of calcium kinetics in calcium and phosphorus deficient rats with the aid of radiocalcium. In FC McLean, P Lacroix, AM Budy (Eds): Radioisotopes and Bone, Blackwell, Oxford, 1962.Google Scholar
- 15.McCollum EV, Simmonds N: Studies on experimental rickets. XV The effect of starvation on the healing of rickets. Johns Hopkins Hosp. Bull. 33: 31–33, 1922.Google Scholar
- 16.Follis HR, Jr.: Diseases, particularly of bone, associated with derangements of calcium and phosphorus metabolism. In Reifenstein FC, Jr. (Ed): Metabolic Interrelations, Transactions of the Fifth Conference, The Josiah Macy, Jr. Foundation, January 5–6, 1953, pp 210–211.Google Scholar
- 19.Beck N: Effect of dietary phosphorus (P) intake on renal actions of parathyroid hormone (PTH) and cyclic AMP (cAMP). Am. Soc. of Nephrology, November 21–23, 1976, Washington, D.C. p1.Google Scholar
- 21.Finkelstein JD, Schachter D: Active transport of calcium by intestine: effects of hypophysectomy and growth hormone. Am. J. Physiol. 203 (5): 873–880, 1962.Google Scholar