Phosphorus adaptation in rats in absence of vitamin D or parathyroid glands.
Growing rats even when vitamin D deficient became adapted to inorganic phosphorus (Pi) deficiency by increasing absorption and minimizing excretion. Feeding low-Pi diet for 3 wk reduced urinary Pi by 80% (P < 0.001), and urinary 32P by 50% (P < 0.001). Low-Pi regimen increased 32p absorption from a 32P-labeled meal by 50% (P < 0.001), even when the animals were vitamin D deficient or thyroparathyroidectomized. The marked increase in retention of 32P in phosphorus-deficient rats could not be accounted for by decreased endogenous intestinal excretion plus increased kidney reabsorption; increased intestinal absorption played a part. 32P absorption was significantly reduced (P < 0.001) by vitamin D deficiency in rats fed either control diet (.6%) Pi or low-Pi diet (0.03%). Endogenous intestinal or urinary excretion of 32P was unaltered by vitamin D deficiency. The evidence supports the hypothesis that there are two mechanisms for phosphorus adaptation: kidney retention not requiring vitamin D, and inreased intestinal absorption of Pi not requiring parathyroids, thyroids, or vitamin D.
D000222:Adaptation, Physiological; D000818:Animals; D007408:Intestinal Absorption; D008297:Male; D010280:Parathyroid Glands / Q000502:physiology*; D010758:Phosphorus / Q000378:metabolism*; D051381:Rats; D013961:Thyroid Gland / Q000502:physiology; D014807:Vitamin D / Q000502:physiology*
D014807:Vitamin D; D010758:Phosphorus