Circadian rhythm of glomerular filtration rate in patients after kidney transplantation

Within 6 months of a kidney transplantation the graft can be regarded as an organ deprived of its innervation. We analysed whether the transplanted kidney has a diurnal rhythm of its glomerular filtration rate (GFR) similar to the GFR rhythm that has been demonstrated in normal individuals and in patients with nephrotic syndrome. GFR was measured by inulin clearances every 3 h during 1 day of bed-rest and identical food and fluid intake per 3 h in seven patients, 4-7 months after a successful kidney transplantation, and in 10 healthy volunteers. Similar to these healthy subjects, a normal circadian rhythm of GFR was detected in all but one patient with a maximum of 57 (range 45-82) ml/min in daytime, a minimum of 47 (range 36-70) ml/min during the night and a relative amplitude of 21 (range 10-41)%. The circadian rhythm of GFR was absent in the patient with the lowest value of GFR (39 ml/min). In conclusion, GFR has a circadian rhythm in patients studied within 6 months of a kidney transplantation, despite the absence of renal innervation.