The complex role of XXXX in the regulation of glomerular ultrafiltration.

@entity15540 @entity1024 @entity2821 @entity842 @entity143
The complex role of @entity842 in the regulation of glomerular ultrafiltration. @entity842 is an important neurohumoral modulator of glomerular ultrafiltration and renal hemodynamics. Multiple @entity842 synthase (NOS) isoforms are present within the kidney. However, it is difficult to discern which NOS is most active from prior studies using non-selective NOS blockers. It is recently apparent that NOS activity is important to the activity of tubuloglomerular feedback (TGF) systems, systems that relate tubular reabsorption to the regulation of glomerular ultrafiltration. Neuronal (nNOS) or brain NOS ( @entity2821 ; NOS I) is present within the macula densa, the sensing element of TGF systems. Inhibition of NOS activity and specifically @entity2821 enhances TGF activity. The TGF system also adapts temporally and these events appear to be dependent upon up-regulation of activity of @entity2821 within the kidney. Temporal adaptation occurs within one to three hours whereby activation of TGF is followed by a gradual return of the glomerular filtration rate (GFR) and renal blood flow toward normal levels. After 24 hours of @entity15540 treatment and withdrawal of this agent, glomerular filtration actually increases to supranormal levels and this is prevented by inhibition of @entity2821 activity. Factors regulating @entity2821 activity have not been fully clarified. We have recently observed @entity1024 ( @entity143 ) receptors within the kidney that, when inhibited, result in major reductions in renal blood flow and GFR, suggesting an important role for the @entity143 receptor in regulation of renal hemodynamics. Future studies will determine whether @entity143 receptor is also an important regulator of @entity2821 activity and the TGF system.
