Renal arteriovenous shunting in rejecting allograft, hydronephrosis, or haemorrhagic hypotension in the rat

Abstract

We studied the occurrence of arteriovenous (A-V) shunting in three experimental rat models, namely in rejecting allograft kidney, in uni- or bilateral ureteral obstruction, and in haemorrhagic hypotension. Isografted or sham-operated rats served as controls. Radiolabelled microspheres were injected into the renal artery and the increase in the amount of radioactivity in the lungs was considered to reflect A-V shunting in the kidney. In animals exposed to haemorrhage, with a blood pressure not less than 70% of the initial blood pressure, practically no shunting was seen. When animals were bled to a hypotension beyond the autoregulation, A-V shunting occurred inversely correlated to the degree of hypotension. In ureteral obstruction, a less marked but significant 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 demonstrated. Histologically, microspheres were found in afferent arterioles less frequently in kidneys with A-V shunting than in controls. These results indicate that A-V shunting is involved in haemorrhagic hypotension, renal graft rejection, and hydronephrosis. In the latter situation A-V shunting is probably regulated by a humoral factor.