Changes in phosphorus distribution during total parenteral nutrition.

To investigate the mechanism of hypophosphatemia during total parenteral nutrition (TPN), changes in phosphate (P) contents in the liver and muscle of rats supported by TPN for 2 days at 270 cal/g were studied in 39 Sprague Dawley rats (200 g body weight), divided into 5 groups as follows: G-I: starved for 24 hr (n = 7); G-II: TPN (5 mEq P/1000 cal) after 24 hr starvation (n = 7); G-III: starved for 4 days (n = 7); G-IV: TPN (5 mEq P/1000 cal) after 4 days starvation (n = 9); G-V: TPN (35 mEq P/1000 cal) after 4 days starvation (n = 9). P contents of the tissues were measured colorimetrically. Results indicated that muscle P content decreased in the depleted rat supported by TPN with low P intake, while an increase in P content in the liver was a constant finding in each TPN group. Increase in P intake tended to preserve the P content in the muscle. These findings suggest that the changes in P distribution in major body tissues must be considered in addition to the changes in the serum inorganic P levels to evaluate an adequate P requirement for TPN.