RENAL ARTERIOVENOUS SHUNTING IN REJECTING ALLOGRAFT, HYDRONEPHROSIS, OR HEMORRHAGIC HYPOTENSION IN THE RAT

We studied the occurrence of arteriovenous (A-V) shunting in three exp erimental rat models, namely in rejecting allograft kidney, in uni- or bilateral ureteral obstruction, and in haemorrhagic hypotension. Isog rafted or sham-operated rats served as controls. Radiolabelled microsp heres were injected into the renal artery and the increase in the amou nt of radioactivity in the lungs was considered to reflect A-V shuntin g in the kidney. In animals exposed to haemorrhage, with a blood press ure not less than 70% of the initial blood pressure, practically no sh unting was seen. When animals were bled to a hypotension beyond the au toregulation, A-V shunting occurred inversely correlated to the decree of hypotension. In ureteral obstruction, a less marked but significan t increase in shunting of microspheres to the lungs was found after 24 h of unilateral obstruction, irrespective of whether the spheres were injected into the obstructed or the contralateral kidney. Significant A-V shunting during the allograft rejection process was also demonstr ated. Histologically, microspheres were found in afferent arterioles l ess frequently in kidneys with A-V shunting than in controls. These re sults indicate that A-V shunting is involved in haemorrhagic hypotensi on, renal graft rejection, and hydronephrosis. In the latter situation A-V shunting is probably regulated by a humoral factor.