Renal Response to Alterations in Dietary Phosphate in the Young Beagle

Abstract

Hyperphosphatemia is present in the young of many species compared to adult animals. We studied the renal response to alterations in dietary phosphate in 4- to 7-day-old beagle puppies. Puppies were phosphate restricted with oral aluminum hydroxide gel (Group I) or phosphate loaded with oral sodium phosphate (Group II). Puppies in both groups had hyperphosphatemia (Group I 8.6, Group II 12.2mg/dl) relative to adult dogs (3.4–4.8 mg/dl). Plasma phosphate concentration (P) and rate of excretion of phosphate (Ep) were independent of glomerular filtration rate (GFR). At any filtered load of phosphate Ep was greater and rate of reabsorption less in Group II independent of P. The maximal rate of phosphate reabsorption (TmP) was higher in Group I (100 μg/ml GFR) than Group II (26 μg/ml GFR). Negative values for phosphate reabsorption in 4 animals support the presence of a secretory mechanism for phosphate. Relative hyperphosphatemia in the puppy is not secondary to a renal limitation in phosphate excretion. The 1- to 2-week-old puppy adjusts renal reabsorption of phosphate to maintain a concentration of phosphate in plasma higher than in the adult animal. The renal alterations in response to variations in dietary phosphate occur independently of plasma phosphate concentration, GFR, or filtered load of phosphate.

Clinical manifestations, response to treatment, and clinical outcome for Weimaraners with hypertrophic osteodystrophy: 53 cases (2009–2011)

“…Similar to results reported elsewhere, 5,[9][10][11][12][13] abnormal CBC and biochemical values in the present study were nonspecific or, in the case of hyperphosphatemia and elevated alkaline phosphatase activity, are routinely detected in juvenile animals. 19,20 The underlying mechanism for HOD is unknown, and the complex manifestation of the disease, including variation in the presence and severity of the clinical signs, suggests a multifactorial cause, such as that observed for immune-mediated disorders. 13 Further support for an immune mechanism in which an immature immune system is mounting a severe sterile inflammatory reaction is the strong positive response to immunosuppressive doses of corticosteroids.…”

“…7 Nonspecific hematologic findings include leukocytosis characterized by neutrophilia and monocytosis as well as mild nonregenerative anemia, thrombocytosis, or thrombocytopenia. 9,10,12 Serum biochemical analysis may reveal hyperphosphatemia and an elevated alkaline phosphatase activity, which is characteristic of juvenile animals, 19,20 together with nonspecific findings such as hypoalbuminemia and low BUN and creatinine concentrations. 9,10,12 Diagnosis of HOD is made on the basis of the medical history, clinical signs, and signalment and by ruling out infectious causes.…”

Ontogeny of renal phosphate transport and the process of growth

“…Experiments performed on dogs [8] and rats [9] provided suggestive evidence that this high reabsorptive capacity is intrinsic to the kidneys. That this is indeed the case was demonstrated by studies performed by Johnson and Spitzer [10] on isolated kidneys of guinea pigs perfused in vitro with solutions containing Pi in concentrations varying between 3 and 15 mg/dl.…”

Fractional excretion tests: a critical review of methods and applications in domestic animals

“…In phosphate‐depleted dogs, FE P was about 10 times lower than that in controls, whereas FE Ca was 4 times higher, and FE Na was identical 34 . In phosphate‐restricted puppies, mean FE P decreased from 60% to 25% 35 . When dogs received an i.v.…”