The glomerular filtration rate of isogeneically transplanted rat kidneys.

The glomerular filtration rate (GFR) was determined in rats with an isogeneic kidney transplant and compared with that of unilaterally nephrectomized rats. Experiments were carried out in adult rats, 3 months of age, weighing approximately 300 g, as well as in juvenile rats, 6 to 8 weeks of age, weighing approximately 170 g. All donor kidneys were taken from adult rats. The GFR was measured regularly, using a chromium 51-EDTA clearance technique which permitted repeated measurements to be taken in the same animals, during a 15-week followup period. After unilateral nephrectomy the GFR per 100 g body weight (BW) increased compared with that of a single normal kidney. Adult transplant recipients had a GFR per 100 g BW of about 80% of that of unilaterally nephrectomized rats. There was no statistical difference in the GFR when comparing adult recipients of either a normal or a hyperfunctional kidney. When isografts were transplanted to juvenile recipients, there was an initial decrease in the absolute GFR compared with the donor value in the case of a normal adult donor kidney. This decrease was even more pronounced when a hyperfunctioning kidney was transplanted to a juvenile recipient. However, when related to BW the GFR was, as in the adult recipients, about 80% of that of unilaterally nephrectomized juvenile rats. During the followup period the systolic blood pressure was measured regularly by tail plethysmography, in order to detect any blood pressure elevations, which are a frequent complication in adult and pediatric human renal transplantation. However, no hypertension was observed after isogeneic kidney transplantation in the various groups. These results show that the GFR of isogeneically transplanted rat kidneys amounts to about 80% of the maximally attainable level. Isogeneic transplantation of an adult kidney to a juvenile recipient results in a rapid adaptation of the GFR to the smaller size of the body and does not cause an increase in blood pressure.