Dietary phosphate-dependent growth is not mediated by changes in plasma phosphate concentration

The present study was undertaken in order to assess the role of dietary pho sphate in growth. A diet deficient in phosphate led to a suppression of gro wth in juvenile rats. The phenomenon is similar to that described for diets deficient in other essential single components such as Mg, Zn or K. Howeve r, unlike the other constituents, dietary phosphate restriction affected th e growth rate much more than it altered the serum phosphate concentration; addition of phosphate to the drinking water of rats fed a low-phosphate die t restored the growth rate without a concomitant change in serum phosphate concentration. The suppression of growth rate by the deletion of phosphate was associated with a delayed decrease in food intake. This finding implies that the variation in appetite was secondary to the change in growth. The increase in body weight following phosphate supplementation was associated with a concomitant increment in food intake. The phosphate-dependent growth was, however, evident also in rats that were pair-fed with those that were not supplied with phosphate. It is concluded that dietary phosphate-depend ent growth is not mediated by changes in phosphate concentrations in the ex tracellular fluid. It is plausible that signals arising from receptors for phosphate in the digestive system constitute part of the growth control app aratus in rats.