Mechanisms of phosphate transport in sheep intestine and parotid gland: response to variation in dietary phosphate supply

Shirazi-Beechey, Soraya P.; Beechey, R. B.; Penny, Jeffrey; Vayro, Steven; Buchan, William; Scott, D.

doi:10.1113/expphysiol.1991.sp003489

Cited by 29 publications

(23 citation statements)

References 31 publications

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“…Similar increases of intestinal active Pi absorption in response to P reduced diets have also been reported for sheep and goats. However, they were not related to changes of the vitamin D endocrine system (SHIRAZI-BEECHEY et al, 1991;SCHRODER et al, 1995). From this it may not be concluded that in ruminants P depletion does not induce any adaptational processes of the hormone-receptor system, since the physiological effect of a hormone may also be exerted by respective changes of the receptor binding properties in target tissues.…”

Section: Discussionmentioning

confidence: 75%

Binding Properties of Goat Intestinal Vitamin D Receptors as Affected by Dietary Calcium and/or Phosphorus Depletion

Schröder

Pfeffer

Failing

et al. 1995

Journal of Veterinary Medicine Series A

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Summary The binding capacity (Bma) and the affinity (Kd) of the intestinal vitamin D receptor (VDR) have been studied using mucosa preparations from the duodenum, jejunum and proximal colon of male growing goats which had been kept in a two‐factorial (2 × 2) trial on Ca and/or P deficient diets for 9 weeks. This treatment resulted in significant changes of different parameters of Ca and P homeostasis. Irrespective from the level of Ca intake, P depletion caused significant hypophosphatemia with corresponding hypercalcemia. In both Ca depleted groups the calcitriol concentrations in plasma significantly increased by more than 100% in comparison with normal Ca supply. No changes were recorded for plasma calcitriol concentrations in response to P depletion with an adequate Ca supply. Plasma PTH levels were only increased significantly in Ca depletion with adequate P supply. Irrespective of different feeding regimens, the highest Bmax values were found in the jejunum. In all intestinal segments tested, the Bmax values were significantly decreased by P depletion as compared with an adequate P supply. No effects on the Bmax of VDR were observed in response to changes of Ca supply. The Kd values of the VDR were neither affected by different intestinal localizations nor by Ca and/or P depletion. From the present results, it has to be concluded that the physiological relevance of VDR down‐regulation may not be related to P homeostasis rather than to Ca homeostasis by minimizing the hypercalcemia induced by P depletion.

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Section: Discussionmentioning

confidence: 75%

Binding Properties of Goat Intestinal Vitamin D Receptors as Affected by Dietary Calcium and/or Phosphorus Depletion

Schröder

Pfeffer

Failing

et al. 1995

Journal of Veterinary Medicine Series A

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“…Em contraste com o nível de Ca, que permanece constante no cristal, os íons fosfato podem ser substituídos por carbonatos (LEGROS et al, 1987). Aumento na razão Ca/P, na deficiência de P, também foi descrito por SHIRAZI-BEECHEY et al (1991) e WAN ZAHARI et al (1990, em carneiros.…”

Section: Resultsunclassified

“…Ambas a composição química e a estrutura do osso são afetadas na deficiência de P. Existem indicações de redução da formação de osso em ovinos (CORLETT e CARE, 1988;SCOTT et al, 1994) e da mineralização do osso em ovinos (SHIRAZI-BEECHEY et al, 1991;TERNOUTH et al, 1993;e SCOTT et al, 1997) e bovinos (SHUPE et al, 1988). A deficiência de P também tem sido associada ao balanço negativo de P (TERNOUTH e SEVILLA, 1990;SHIRAZI-BEECHEY et al, 1991;e BORTOLUSSI et al, 1996) e aumento na excreção de piridinolina e deoxipiridinolina (SCOTT et al, 1997), em ruminantes, indicando reabsorção do osso e/ou perda de P dos tecidos moles.…”

Section: Resultsunclassified

“…A deficiência de P também tem sido associada ao balanço negativo de P (TERNOUTH e SEVILLA, 1990;SHIRAZI-BEECHEY et al, 1991;e BORTOLUSSI et al, 1996) e aumento na excreção de piridinolina e deoxipiridinolina (SCOTT et al, 1997), em ruminantes, indicando reabsorção do osso e/ou perda de P dos tecidos moles.…”

Section: Resultsunclassified

“…Uma explicação para o equilíbrio nos níveis de Pi plasmáticos nos novilhos deficientes, embora em patamares inferiores, é a capacidade de adaptação de ruminantes à deficiência de P, por intermédio de mecanismos como o aumento da eficiência de absorção do P no intestino (SHIRAZI-BEECHEY et al, 1991;COATES e TERNOUTH, 1992).…”

Section: Nicodemo Et Alunclassified

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Uso de parâmetros ósseos, plasmáticos e fecais na determinação da deficiência de fósforo em bovinos

et al. 2000

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RESUMO -Quinze novilhos Nelore foram distribuídos em três tratamentos, consistindo de dieta basal capaz de proporcionar ganhos da ordem de 600 g/dia, suplementada (15 ou 11 g P/dia) ou não (5 g P/dia) com fosfato monoamônico, para determinar as alterações provocadas por deficiência de P em parâmetros ósseos, sangüíneos e fecais. Biópsias de costela foram obtidas aos 60 e 250 dias de experimentação. Amostras de plasma foram coletadas quinzenalmente e amostras de fezes retais, analisadas em sete ocasiões, durante os 250 dias do experimento. Coleta total (diária) de fezes foi feita em dois períodos, aos 60 e 243 dias, durante sete dias. Aos 60 dias, P expresso em relação ao osso fresco, osso seco e desengordurado e ao volume de osso discriminaram entre os tratamentos. Aos 250 dias, a espessura da camada cortical e as concentrações de cinzas e fósforo foram reduzidas na deficiência de P. Observou-se queda na concentração de fósforo inorgânico plasmático (Pi), já aos 12 dias de experimentação, apresentando valores em torno de 3,0 mg % na época em que ganho de peso foi afetado (82 dias). Foi observada elevação do Ca e da fosfatase alcalina na deficiência de P, sem alterações na concentração de hidroxiprolina do plasma. As concentrações de P nas fezes aumentaram com a concentração do elemento na dieta, mas a utilização de amostras coletadas do reto não propiciou detecção precoce de deficiência de P. A definição de níveis críticos para a determinação de deficiência apresentou problemas.Palavras-chave: bovinos, deficiência, fósforo, níveis críticos, osso, plasma Use of Bone, Plasma and Feces in the Assessment of P Status in CattleABSTRACT -Fifteen Nellore steers were allotted to three treatments, consisting of a basal diet, which will be able to provide gains of about 600 g/day, supplemented (15 or 11 g P/day) or not (5 g P/day) with monoammonium phosphate in order to evaluate the alterations in bone, plasma and fecal measurements due to P deficiency. Rib biopsies were taken at 60 and 250 days of trial, plasma samples were taken every 15 days, and fecal grab samples were analyzed in seven occasions along the trial. Total daily fecal collection was performed in two occasions, at 60 and 243 days of the trial, for seven days. At day 60, P expressed as fresh bone, dried defatted bone and bone volume were able to detect treatment differences. At day 250, cortical thickness, P and ash concentrations were reduced in P deficiency. Plasma inorganic P (Pi) was lower at 12 days of trial, with values close to 3,0 mg % at the time where daily weight gain was affected (day 82). Calcium and total alkaline phosphatase increased in P deficiency, without changes on the plasma hidroxyproline concentration. Fecal P concentrations increased as the dietary P concentrations increased, but grab samples did not allow early detection of P deficiency. The definition of critical P levels for the determination of deficiency showed problems.

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Mechanisms of phosphate uptake into brush-border membrane vesicles from goat jejunum

Schröder

Breves

1996

J Comp Physiol B

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This study concerns the uptake of inorganic phosphate into brush-border membrane vesicles prepared from jejunal tissues of either control or Ca- and/or P-depleted goats. The brush-border membrane vesicles showed a time-dependent accumulation of inorganic phosphate with a typical overshoot phenomenon in the presence of an inwardly direct Na+ gradient. The Na+-dependent inorganic phosphate uptake was completely inhibited by application of 5 mmol.1(-1) sodium arsenate. Half-maximal stimulation of inorganic phosphate uptake into brush-border membrane vesicles was found with Na+ concentrations in the order of 5 mmol.1(-1). Inorganic phosphate accumulation was not affected by a K+ diffusion potential (inside negative), suggesting an electroneutral transport process. Stoichiometry suggested an interaction of two or more Na ions with one inorganic phosphate ion at pH 7.4 Na+-dependent inorganic phosphate uptake into jejunal brush-border membrane vesicles from normal goats as a function of inorganic phosphate concentration showed typical Michaelis-Menten kinetic with Vmax = 0.42 +/- 0.08 nmol.mg-1 protein per 15S-1 and Km = 0.03 +/- 0.01 mmol.1(-1) (n = 4, mean +/- SEM). Long-term P depletion had no effect on these kinetic parameters. Increased plasma calcitriol concentrations in Ca-depleted goats, however, were associated with significant increases of Vmax by 35-80%, irrespective of the level of P intake. In the presence of an inwardly directed Na+ gradient inorganic phosphate uptake was significantly stimulated by almost 60% when the external pH was decreased to 5.4 (pHout/pHin = 5.4/7.4). The proton gradient had no effect on inorganic phosphate uptake in absence of Na+. In summary, in goats Na+ and calcitriol-dependent mechanisms are involved in inorganic phosphate transport into jejunal brush-border membrane vesicles which can be stimulated by protons.

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Mechanisms of phosphate transport in sheep intestine and parotid gland: response to variation in dietary phosphate supply

Cited by 29 publications

References 31 publications

Binding Properties of Goat Intestinal Vitamin D Receptors as Affected by Dietary Calcium and/or Phosphorus Depletion

Binding Properties of Goat Intestinal Vitamin D Receptors as Affected by Dietary Calcium and/or Phosphorus Depletion

Uso de parâmetros ósseos, plasmáticos e fecais na determinação da deficiência de fósforo em bovinos

Mechanisms of phosphate uptake into brush-border membrane vesicles from goat jejunum

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