Physiology

• What is the focus of integrative renal physiology?

  Measuring renal function in vivo
• What is the purpose of exposing the kidney in an anaesthetized animal?

  To measure renal function in vivo
• What does a healthy kidney show in structural and functional imaging?

  Arterioles that light up the kidney indicating high blood flow
• How does hypertension affect kidney perfusion?

  It leads to poorly perfused regions and atrophy in parts of the kidney
• What happens to blood pressure during sleep?

  Blood pressure falls, known as nocturnal dip
• What condition can lead to the loss of nocturnal dip in blood pressure?

  Diabetes
• What does the forearm blood flow experiment help to understand?

  The relationship between structural and functional imaging and human physiology
• What are the key aspects of renal physiology studied in this context?

  • Haemodynamics: Renal Blood Flow / Glomerular filtration
  • Renal Tubule Function: Sodium (Na) and Potassium (K) handling
  • Integration & Balance
• What percentage of cardiac output does the kidney receive?

  ~20%
• How does kidney perfusion compare to that of the heart and brain?

  The kidney has a higher perfusion rate than the heart and brain per gram
• What is the purpose of renal autoregulation?

  To control its own blood supply and buffer tissue perfusion
• Which organs have strong autoregulation?

  The heart, brain, and kidney
• What happens to the glomerular filtration rate (GFR) when blood enters the kidney?

  The GFR is lower because blood is filtered
• What is the autoregulatory range of kidney perfusion?

  It remains stable across a large range of blood pressure
• Why is autoregulation important for the kidney?

  It maintains stable organ perfusion despite acute blood pressure changes
• What occurs during exercise regarding blood pressure and GFR?

  If blood pressure to the kidney increases, GFR also increases, leading to excessive plasma filtration
• What is the mechanism of autoregulation in the kidney?

  • Myogenic reflex of renal vasculature
  • Stretch of artery leads to constriction
  • Extracellular ATP release activates P2X1 receptors
  • Increases intracellular [Ca2+]i causing contraction
• What happens when stretch increases in renal vasculature?

  It causes the release of ATP
• What is the effect of extracellular ATP on renal arteries?

  It constricts renal arteries and arterioles
• How do afferent arterioles respond to increasing ATP?

  They constrict in response to stretch
• What happens to P2X1R knockout (KO) mice regarding vasoconstriction?

  They do not have vasoconstriction and vessel diameter increases
• What is the pO2 in the cortex of the kidney?

  ~80 mmHg
• What is the pO2 in the medulla of the kidney?

  ~10 mmHg
• What happens if pO2 declines further than 10 mmHg in the kidney?

  It can cause damage and inflammation
• Why is high blood flow important for the kidney?

  It supports glomerular filtration needed to filter blood from byproducts
• What drives ultrafiltration in the kidney?

  • Hydrostatic pressure favors filtration
  • Oncotic pressure opposes filtration
• What are the components of the glomerular filtration barrier?

  Podocytes, glomerular basement membrane, endothelial cells
• How does charge influence filtration in the kidney?

  Negative charge influences filtration, with cations being more filterable than anions above 1.6 nm
• What happens to filtration with molecular radius greater than 1.6 nm?

  Filtration decreases for molecules larger than 1.6 nm
• What is the consequence of losing key proteins in the filtration barrier?

  It can lead to nephrotic syndrome
• What is the typical filtration rate in the kidney?

  ~120 ml/min
• How much fluid does the kidney filter daily?

  ~180 L/day
• What are the mechanisms of autoregulation in the kidney?

  • Tubuloglomerular feedback (TGF)
  • Paracrine signaling within the juxtaglomerular apparatus
• What is the role of the macula densa in autoregulation?

  • Senses chloride increase through NKCC2
  • Releases ATP to adjust afferent arteriole constriction
• What is the function of the proximal convoluted tubule?

  It reabsorbs ~65% of Na, K, bicarbonate, phosphate, and 100% of glucose and amino acids
• What is glomerulotubular balance (GTB)?

  It adjusts to changes in single-nephron GFR to prevent distal tubule overload
• What is the reabsorption rate of sodium and water in the proximal convoluted tubule?

  It reabsorbs sodium and water at an isosmotic balance
• What happens in the distal tubule and cortical collecting tubule regarding reabsorption?

  They have limited capacity for reabsorption
• What is the role of the principal cell in the cortical collecting tubule?

  • Na/K handling
  • Regulated by the renin-angiotensin-aldosterone system
• What is the effect of mutations in ENaC?

  Loss of function leads to low blood pressure, while gain of function leads to hypertension