title: Adaptive responses of calcium and phosphate homeostasis in goats to low nitrogen intake: renal aspects.
abstract: In a previous study, in goats, we showed that apart from variations in dietary calcium (Ca) and phosphorus intake, also low dietary nitrogen (N) intake altered plasma concentrations of hormones, which regulate Ca and phosphate (Pi ) homeostasis. These hormonal responses in goats were in accordance with findings in monogastric animals and humans with low protein intake. In the aforementioned studies, alterations of electrolyte transport in the kidneys were also observed. However, whether renal electrolyte transport in goats is also involved in the adaptation of Ca and Pi homeostasis to low N intake remains unknown. Thus, the aim of the present study was to investigate whether in addition to the hormonal changes, as observed in our former study, renal Ca transport and renal Pi transport were also altered by low N intake in goats. Therefore, in kidney samples from the goats used in our former study, the protein expression of Ca and Pi transporters and of related regulatory proteins was examined. Furthermore, the uptake of Pi into isolated brush border membrane vesicles (BBMV) was detected. The results showed that the protein amount of the renal sodium-dependent Pi transporter NaPi IIa was elevated, and concomitantly, protein expression of its upstream regulators, the parathyroid hormone receptor and the extracellular signal-regulated kinases 1 and 2 was decreased. However, Pi uptake into renal BBMV was not enhanced. Furthermore, protein expression of the renal Ca channel, the transient receptor potential cation channel subfamily V member 5 (TRPV5) and of the vitamin D receptor was not influenced by dietary N reduction. We conclude that regulation of renal Pi transporter expression in goats is involved in the adaptation of electrolyte homeostasis to low N intake.
authors.affiliation: Department of Physiology, University of Veterinary Medicine Hannover, Hannover, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Starke
authors.forename: K
authors.initials: K
authors.lastname: Huber
mesh_terms: D000821:Animal Feed / Q000032:analysis*; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004032:Diet / Q000662:veterinary; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000502:physiology; D006041:Goats; D007668:Kidney / Q000378:metabolism*; D009584:Nitrogen / Q000008:administration & dosage* / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism*; D044168:Receptor, Parathyroid Hormone, Type 1 / Q000235:genetics / Q000378:metabolism; D050608:Sodium-Phosphate Cotransporter Proteins / Q000235:genetics / Q000378:metabolism; D050916:TRPV Cation Channels / Q000235:genetics / Q000378:metabolism
chemical_list: D010710:Phosphates; D044168:Receptor, Parathyroid Hormone, Type 1; D050608:Sodium-Phosphate Cotransporter Proteins; D050916:TRPV Cation Channels; D048049:Extracellular Signal-Regulated MAP Kinases; D009584:Nitrogen; D002118:Calcium
keywords: NaPi IIa; kidney; phosphate transport; renal electrolyte transport