INVERSE RELATION BETWEEN PLASMA INORGANIC-PHOSPHATE AND PHOSPHOLIPIDS IN MICE - EFFECT OF DIETARY INORGANIC-PHOSPHATE, FASTING AND GLUCAGON

We measured in mice under various conditions plasma phospholipids (Plip(Pl)), total phosphate (Ptot(Pl)), inorganic phosphate (Pi(Pl)), and calculated other phosphate-containing material (PX(Pl)) by subtracting (Plip + Pi)Pl from Ptot(Pl). In mice fed low Pi diet (LPD) for 10 days, Plip(Pl) was higher, PX(Pl) did not change, whereas Pi(Pl) and Ptot(Pl) were lower than under high Pi diet (HPD). A highly significant inverse correlation was found between Plip(Pl) and Pi(Pl). The effect on Plip(Pl) of maneuvers known to change Pi(Pl) acutely (within hours) was then investigated. In LPD mice, 6 h fasting, which increases Pi(Pl), led to a decrease of Plip(Pl) without significant changes of Ptot(Pl) and PX(Pl). The conspicuous rise in Pi(Pl) observed with glucagon treatment was associated with a decrement of Plip(Pl) of the same magnitude as the increase in Pi(Pl) without a change of Ptot(Pl) or PX(Pl). Finally, injection of Pi lowered Plip(Pl) in a dose-dependent manner within 2 h. In mice fed HPD, Plip(Pl) decreased similarly during all acute maneuvers described under LPD, except Pi injection, where it did not decrease. In conclusion, the effects described above would suggest that the regulation of the two phosphate species may be linked and that Plip(Pl) may possibly be involved in Pi homeostasis.