Curci S, Casavola V, Lippe C
Arch Int Physiol Biochim. 1978 May;86(2):243-50. doi: 10.3109/13813457809069901.
Counterflow experiments demonstrate the existence of urea counter-transport on the epithelium luminal surface. This phenomenon disappears when 10(-4) M phloretin is added to the perfusion fluid. Moreover counterflow experiments made using thiourea as elicitor, demonstrate that the phenomenon is specific for the urea.