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Calcium and Phosphorus Metabolism in Pregnant Rats Ingesting a High Protein Diet^1,2,3,

Nutrition Program, College of Human Development, The Pennsylvania State University, University Park, PA 16802 and Department of Human Development and Consumer Sciences, University of Houston, Houston, TX 77004

In both nonpregnant and pregnant rats as dietary protein increased, increases in urinary calcium were observed. In nonpregnant rats, urinary calcium excretion was significantly increased as the level of dietary protein increased from 16 to 24 to 32%, but in the pregnant rats increases in urinary calcium as protein intake was raised from 24 to 32% were not observed. The present data indicated that the increase in urinary calcium was probably a result of a shift of the endogenous excretion of calcium from the feces to urine and not from intestinal absorption of dietary calcium or bone resorption of calcium. Responses of parameters indicative of intestinal absorption either were inconsistent or were not affected as protein intake increased. A high protein diet had no effect on the amount of calcium lost from the bones. Although the results were inconsistent with regard to calcium retention, a positive calcium balance was achieved by all rats fed the three different levels of dietary protein. Urinary phosphorus excretion increased with increased protein intake, but the response was modified by the physiological state. In pregnant rats, the increase from 16 to 24% dietary protein had a greater influence on urine phosphorus than the increase from 24 to 32%; this pattern was reversed in the nonpregnant rats.

KEY WORDS: • high protein • pregnancy • calcium phosphorus

¹ Preliminary report: Graves, K. L. & Wolinsky, I. (1978) Calciuretic effect of dietary protein in pregnant and virgin rats. Fed. Proc. 37, 847 (abs.).

² Paper no. 5916 in the Journal Series of the Pennsylvania Agricultural Experiment Station.

³ Supported in part from funds from the Pennsylvania Agricultural Experiment Station and Grant AGO2396, N.I.H.

⁴ In partial fulfillment of the requirements for the Ph.D. degree.

⁵ To whom reprint requests should be sent: Dept. Human Development and Consumer Sciences, 225 Cameron Building, University of Houston, Houston, TX 77004.

Manuscript received 14 March 1980.