Adaptive increase in phytate digestibility by phosphorus-deprived rats and the relationship of intestinal phytase (EC 3.1.3.8) and alkaline phosphatase (EC 3.1.3.1) to phytate utilization.

1. The effects of phosphorus deprivation on phytate digestibility, phosphorus utilization and intestinal phytase (EC 3.1.3.8) and alkaline phosphatase (EC 3.1.3.1) in rats were investigated. 2. P deprivation was achieved by giving rats a diet containing 3 g P/kg and resulted in hypophosphataemia, hypercalcaemia, hypercalciuria, and lower levels of P absorbed and retained, and calcium retained. 3. Rats adapted to P deprivation by increasing the digestion of total dietary-P and phytate-P. 4. Levels of intestinal alkaline phosphatase and alkaline phytase were not different between the two treatment groups. 5. P deprivation in the rats given the marginal-P diet may be a result of a lower absorption of total dietary-P or increased absorption of inositol phosphates formed during the enzymatic hydrolysis of phytate which are not readily utilized by the rat. 6. These results suggest that intestinal phytase and alkaline phosphatase do not play a role in the adaptive increase in phytate digestibility by rats given marginal-P diets. The adaptation may result from enhanced phytase or alkaline phosphatase synthesis by the gastrointestinal microflora stimulated by a lower level of P in the digesta.