Expansion
Autoregulation and hormonal control persist, but neural reflexes are lost
Expansion
Preserved after denervation
- Myogenic autoregulation
- Tubuloglomerular feedback
- Renin release in response to reduced afferent arteriolar stretch and to macula densa signals
- Responses to circulating angiotensin II, aldosterone and antidiuretic hormone
Lost
- Sympathetic vasoconstriction in response to hypovolaemia or exercise
- Direct beta-1 mediated renin release
- Neurally mediated sodium retention
This makes the transplanted kidney relatively vulnerable to hypotension, since it cannot participate in the systemic vasoconstrictor response, and it emphasises how much of renal regulation is intrinsic.
The same physiology underlies renal denervation as a treatment for resistant hypertension: ablating renal sympathetic nerves reduces renin release and sodium retention, and also removes afferent signalling from the kidney to central sympathetic centres.
A transplanted kidney also loses its normal circadian variation in excretion, which is why transplant recipients often have nocturia.