Abstract
The tubuloglomerular feedback mechanism is highly activated in juxtamedullary nephrons and considered to play a major role in intrarenal regulation of glomerular filtration rate. The vasculature of juxtamedullary nephrons is highly vasoreactive with a high ability for vasodilation. This vasoreactivity is a prerequisite for an important influence of the tubuloglomerular feedback mechanism on the medullary blood flow and its regulation.