Sodium gene defect

Several diseases involving dysregulation of MR function have been described although most of them are not causatively linked to the receptor itself. Pseudohypoaldosteronism for example is a syndrome of mineralocorticoid resistance characterized by urinary salt loss and dehydration. However, only very rarely mutations in the MR gene have been found in these patients so far. In most cases, this syndrome appears to be linked to defects in the subunits of the amiloride-sensitive sodium channel ENaC, a major target of mineralocorticoid action in the kidney. 

HCN4 encodes a pacemaker current in sinoatrial nodal cells mutations in sodium channel gene (SCN5A) cause conduction defects. 

Cystic fibrosis—a fatal, hereditary disease characterized by a heavy mucus buildup in the lungs—is caused by a defective plasma membrane protein. In persons with cystic fibrosis this transport protein, known as the sodium-potassium pump, abnormally transports sodium ions across the membrane without carrying the chloride ions that usually accompany them. Research is currently underway to correct through genetic engineering the faulty gene that codes for the plasma membrane protein. 

An example of a disease that results from a deletion mutation is cystic fibrosis. The presence of mutated genes in which three thymine bases are absent produces cells in the lungs that are defective in the transport of molecules such as sodium. A result is the accumulation of mucus in the lungs. Bacteria readily colonize the mucus and become resistant to treatments intended to kill them. As... 

Several disorders of tubular phosphate handhng have been described. The best known of these is X-linked dominant hypophosphatemic rickets (previously known as vitamin D-resistant rickets). This disorder arises because of a defect in the PHEX gene. A defect of the sodium-dependent/ phosphate co-transporter has also been described, giving rise to autosomal recessive hereditary hypophosphatemic rickets with hypercalciuria. The molecular biology of tliese and other renal phosphate transport disorders has been reviewed. ... 

Hypokalemic periodic paralysis Due to defective gene for one type of DHPR. Hyperkalemic periodic paralysis Due to defects in a skeletal muscle sodium channel,... 

As the end result, OP shortens the cycle time of the AP and lessens the amplitude of the mainly sodium current-controlled depotarization spike. The dome of the AP is affected by OP-caused changes in the /u, /xf Ks currents. Block of the /kt current lengthens the QT interval of the ECG, reminiscent of LQT2 caused by a defect in the HERG gene. M cells of the ventricular wall prolong QT more than do the epicardial or endocardial cells. 

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