ABSTRACT
In this study,the effects of hyperosmolality on the expression of urea transporter A2 (UTA2) and aquaporin 2 (AQP2) were investigated in transfected immortalized mouse medullary collecting duct (mIMCD3) cell line.AQP2-GFP-pCMV6 and UTA2-GFP-pCMV6 plasmids were stably transfected into mIMCD3 cells respectively.Transfected mIMCD3 and control cells were cultured in different hypertonic media,which were made by NaCl alone,urea alone,or an equiosmolar mixture of NaCl and urea.The mRNA and protein expression of AQP2 was elevated by the stimulation of NaCl alone,urea alone and NaCl plus urea in AQP2-mIMCD3 cells; whereas NaCl alone and NaCl plus urea rather than urea alone increased the mRNA and protein expression of UTA2 in UTA2-mIMCD3 cells,and all the expression presented an osmolality-dependent manner.Moreover,the mRNA and protein expression of UTA2 rather than AQP2 was found to be synergistically up-regulated by a combination of NaC1 and urea in mIMCD3 cells.It is concluded that NaC1 and urea synergistically induce the expression of UTA2 rather than AQP2 in mIMCD3 cells,and hyperosmolality probably mediates the expression of AQP2 and UTA2 through different mechanisms.
ABSTRACT
On view of the absent or minimal osmotic diuresis in end stage renal disease, hyperglycemia on maintenance hemolysis as compared to nonketotic hyperosmolar status without underlying advanced renal failure has been noted to show a wide clinical spectrum form severe manifestations by hypertonicity to no clinical manifestations at all. We experienced a 60-year-old man with a known history of type 2 diabetes mellitus on maintenance hemodialysis for 2 years, who was admitted 4 times within 1 year with hyperglycemia (>500 mg/dL) accompanied by recurrent nausea and vomiting at each admission. However, the calculated effective osmolality (tonicity) in this case ranged only from 286 to 303 mOsm/kg H2O. During the past 6 months following meticulous education for the importance of compliance to medication, especially prokinetics for diabetic gastroparesis, he developed no further episode of hyperglycemia or nausea and vomiting.