Endocrine Abstracts

Calcium homeostasis is a key element in bone development and in the maintenance of normal bone architecture. Bone acts in conjunction with the kidneys and the parathyroid glands to maintain circulating calcium levels. In times of excess it functions as a reservoir, but it is also able to donate calcium to the body when circulating levels are low and its structure and mineral content vary accordingly. The calcium sensing receptor (CaR) in both the parathyroid glands and in the ...

The active form of vitamin D, 1,25-dihydroxyvitamin D3 (1,25D3), is vital for calcium/phosphate homeostasis, bone cell differentiation and modification of immune responses. Synthesis of 1,25D3 is catalysed by the mitochondrial cytochrome P450 enzyme 25-hydroxyvitamin D3-1α-hydroxylase (1α-OHase; CYP27B1). Although 1α-OHase has been detected at several extra-renal sites, circulating levels of 1,25D3 appear...

The active form of vitamin D, 1,25-dihydroxyvitamin D3 (1,25D3), is a potent regulator of the immune system and activation of the vitamin D receptor alters expression and secretion of cytokines, chemokines and cell adhesion factors. Initial studies suggested that 1,25D3 synthesis and metabolism are increased in renal epithelial cells by TNFα and IL-1β. Therefore, the aim of this study was to examine whether vitamin D alters the expression of immune activated molecule...

Medial calcification is a major cause of premature cardiovascular mortality in chronic kidney disease. Vascular smooth muscle cells (VSMC) play a key role in this process and studies have suggested a protective role for vitamin D. The exact mechanism for this is unclear but local synthesis of 1,25-dihydroxyvitamin D (1,25D) may be important. Production of 1,25D from 25-hydroxvitamin D (25D) is catalyzed by 25-hydroxyvitamin D-1α-hydroxylase (1α-OHase). 1,25D is metab...

Alterations in sodium reabsorption in collecting duct epithelium can have severe implications for the normal function of the nephron and may precipitate the development of secondary hypertension. One of the principal protein kinases involved in sodium transport in the nephron is the serum and glucocorticoid regulated kinase (SGK1) that mediates translocation and insertion of the epithelial sodium channel (ENaC) into the plasma membrane. SGK1 appears to be increased in the kidn...

Background: Transient Receptor Potential (TRP) channels are expressed in many epithelial cells and respond to mechanical or osmotic stress by initiating a number of calcium-dependent mechanisms. The human serum and glucocorticoid regulated kinase (hSGK) is one such calcium-dependent protein found in the kidney. Stimulated by cell shrinkage, this volume-regulated kinase stimulates sodium transport. Aberrant absorption of sodium has been implicated in the development of hyperten...

The active form of vitamin D, 1,25-dihydroxyvitamin D3 (1,25D3), is synthesised by the enzyme 25-hydroxyvitamin D3-1alpha-hydroxylase (1alpha-hydroxylase). The principal site of 1alpha-hydroxylase activity is in the proximal tubule of the kidney. In order to investigate renal vitamin D metabolism we have used a human proximal tubule cell line, HKC-8. We have previously shown that synthesis of 1,25D3 activity in these cells is sensitive to the concentration of calcium and North...