Stretching of glomerular afferent arterioles in the swollen renal allograft undergoing acute rejection.

Marked renal swelling occurs in acute renal allograft rejection. The impaired renal function in this state could be related in part to mechanical adjustments that the renal tubular and vascular network must make as they participate in the overall expansion of renal parenchyma! volume. In the present study we examined whether vascular stretching occurs in the swollen acutely rejecting kidney. From each of five pairs of dogs matched for weight, a donor animal was chosen from which a control kidney was removed, weighed, and perfused at constant pressure (150 mm Hg) with polymerizing silicone rubber. The contralateral kidney was transplanted into the recipient dog which was then bilaterally nephrectomized. On the sixth posttransplant day, the transplant kidney was removed, weighed, and perfused with silicone rubber, as above. Multiple coronal sections were made of each control and transplant kidney and a total of 240 photomicrographs were taken of the coronal sections from unselected fields of outer and inner cortex. The photographic slides were then coded, randomized, and projected. Measurements were then made, from the projected images, of the glomerular afferent arteriolar length (AL), and width (AW), and the glomerular width (GW). The code was then broken and the measurements in the control and transplant kidneys collated. We found that transplant AL was significantly longer (mean ratio: transplant/control •= 1.32 ± 0.06, P < 0.001) and transplant AW significantly narrower (mean ratio: transplant/control 0.88 ± 0.04, P< 0.05). We also found that GW was slightly but significantly decreased in the transplant compared to the control kidney. We conclude that afferent arteriolar stretching occurs in swollen renal allografts and accounts, at least in part, for the impaired renal function observed in acutely rejecting renal allografts. Ore Res 44: 216-222, 1979