Duct cells

The V2R is expressed in collecting duct cells in rodents it is also expressed in cells of the thick ascending limb of Henle s loop (TAL). V2R-induced Gs-mediated activation of AC, the subsequent increase... 

The VACM-1 receptor is a membrane-associated protein with a single putative transmembrane domain that binds selectively AVP (XD — 2 nM), but cannot discriminate between VXR and V2R analogues. It is expressed in endothelial and medullary collecting duct cells and upon stimulation by AVP. It induces a mobilization of cytosolic-free Ca2+, decreases cAMP production and inhibits cellular growth via MAPK phosphorylation and p53 expression. The mechanism of action and physiological functions of this new receptor are not well understood, but it seems to participate in the regulation of AVP induced signal transduction pathways or of a yet unidentified peptide. 

Organic peroxides such as cumene hydroperoxide and t-butyl hydroperoxide have extensively been used as experimental agents. They provoke lipid peroxidation in hepatocytes, probably by the generation of alkoxyl and peroxyl radical intermediates after reaction with cytochrome P450. Other cytotoxic mechanisms are probably involved including protein thiol and non-protein thiol oxidation and deranged calcium homeostasis (Jewell et al., 1986). In fact, the addition of cumene hydroperoxide to isolated bUe duct cells, devoid of cytochrome P450 activity, still results in cell death but lipid peroxidation is not detectable (Parola et al., 1990). 

Ramaswamy, K., Goodman, R.E. and Bell, R.G. (1994) Cytokine profile of protective anti-Trichinella spiralis CD4 0x22- and non-protective CD4+ 0x22+ thoracic duct cells in rats secretion of IL-4 alone does not determine protective capacity. Parasite Immunology 16, 435-445. 

Handlogten, M.E. et al. (2005) Apical ammonia transport by the mouse inner medullary collecting duct cell (mIMCD-3). Am.]. Physiol. Renal Physiol. 289, F347-F358. 

Dworzack, D.L. and Grantham, J.J. (1975). Preparation of renal papillary collecting duct cells for study in vitro. Kidney Int. 8 191-194. 

The antidiuretic hormone is an octapeptide released from the posterior lobe of pituitary gland. It is used in the treatment of diabetes insipidus. ADH reduces the total urine volume and absence of this hormone cause diabetes insipidus. ADH acts on collecting duct cells to increase their water permeability. It acts on V2 receptors in collecting duct and regulate their water permeability through cAMP production. 

Ion transport pathways across the luminal and basolateral membranes of collecting tubule and collecting duct cells. Inward diffusion of Na+ via the epithelial sodium channel (ENaC) leaves a lumen-negative potential, which drives reabsorption of and efflux of K+. (R, aldosterone receptor.)... 

Water transport across the luminal and basolateral membranes of collecting duct cells. Above, low water permeability exists in the absence of antidiuretic hormone (ADH). Below, in the presence of ADH, aquaporins are inserted into the apical membrane, greatly increasing water permeability. (AQP2, apical aquaporin water channels AQP3,4, basolateral aquaporin water channels V2, vasopressin V2 receptor.)... 

Chronic administration causes proliferation of bile duct cells leading to hepatocyte atrophy, fibrous tissue surrounding proliferated bile ducts, and eventually cirrhosis and hepatocellular carcinoma. 

It increases the water permeability of the kidney collecting duct cells by inducing translocation of aqua-porin proteins from intracellular storage vesicles into the apical plasma membrane.78 Vasopressin binds to... 

V1a receptor agonlsm Vasoconstriction 4- kidney medullary blood flow Increased medullary osmolality I V2 receptor agonism t f T Aquaporin-2 levels in renal colleclrig duct cell membranes 1 Increased collecting duct H20-permeability i 1 i... 

Secretin is secreted in response to acid in the duodenum. Its effect on the biliary system is similar to that on the pancreas it simulates biliary duct cells to secrete bicarbonate and water, expanding the volume of bile and increasing the flow rate into the intestine. 

CCK also stimulates the release of sodium bicarbonate and large amounts of fluid from cells of the pancreatic duct. These epithelial cells line the lumen of the duct. The bicarbonate neutralizes gastric acid entering the duodenum through the pylorus. The effect of CCK on the duct cells is described later in this chapter. 

Secretin enters the blo<>dstream and travels to the pancreas, where it stimulates the duct cells lo release bicarbonate and large volumes of fluid into the pancreatic duct The duct cells are located in the walls of the pancreatic duct. This duct leads from the acinar cells of the pancreas to the ampulla of Vater. The bicarbonate neutralizes the gastric acid entering the duodenum, providing an environment suitable for the functioning of enzymes and absorptive processes that re<]uire a neutral pH. 

Logsdon, C. D. (1995). Pancreatic duct cell cultures There is more to ducts than salty water. Gastroentemiogif 109,1005-1009. 

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