Mammalian urea transporters

Area of Science:

• Physiology
• Molecular Biology
• Nephrology

Background:

• Urea is crucial for the kidney's urine-concentrating mechanism.
• Specific urea transporter proteins facilitate urea transport in kidney and red blood cells.
• Two gene families, UT-A and UT-B, and various cDNA isoforms have been identified.

Purpose of the Study:

• To review physiological evidence for facilitated and active urea transport.
• To discuss the molecular biology of urea transporter gene families and cDNAs.
• To summarize integrative studies on urea transporter protein regulation in renal and non-renal tissues.

Main Methods:

• Cloning of urea transporter cDNAs from multiple species.
• Generation of polyclonal antibodies against urea transporter proteins.
• Integrative animal studies using antibodies to investigate protein regulation.

Main Results:

• Vasopressin enhances UT-A1 phosphorylation in rat inner medullary collecting duct.
• Increased UT-A1 protein abundance occurs in rat inner medulla during reduced urine-concentrating ability.
• Urea transporters are present in non-renal tissues; UT-A protein is upregulated in liver and heart in uremia.

Conclusions:

• Facilitated urea transport via UT-A and UT-B proteins is essential for renal function.
• Urea transporter expression and regulation are complex, involving hormonal and pathological influences.
• Further research into urea transporters in both kidney and other organs is warranted.