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Renal 3-4 - Lecture notes

Lecture notes

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Bioscience 1 (CXA204)

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University of Tasmania

Academic year: 2018/2019

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Renal Week 3-

Factors influencing fluid and solute movement in reabsorption and secretion Concentration and gradients   OsmosisDiffusion

Regional specialisations of tubule cells The chemistry of solutes  Polar vs non-polar Presence of suitable channels, transporters and pores  Facilitated diffusion Hormones, drugs can affect permeability

Reabsorption Obligatory reabsorption Occurs in the  Proximal convoluted tubule   Nephron loopDescending limb  Ascending limb Due to physical and chemical properties of the tubule cells and the tubular fluid, not affected by hormones

To this point, reabsorption has been obligatory From this point onward, reabsorption is dictated by the concentrations of hormones in the blood The hormones   Aldosterone – influences Na+ reabsorption and indirectly H20 reabsorptionADH (H20) reabsorption  Parathyroid hormone – sodium phosphate reabsorption, Ca2+ reabsorption DCT and collecting ducts  Is dependant on hormones  Can result in changes in the volume and concertation of the urine  Change in urine volume is one mechanism in the long term regulation of bloodvolume and therefore blood pressure  Changes in blood volume (and therefore blood pressure) will induce compensatory changes in renal function

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Aldosterone A mineralocorticoid released from the adrenal cortex in response to  Angiotensin 2 (if BP falls)  Decreased Na+ (hyponatremia)  Increased K+ (hyperkalemia) Stimulates Na+ reabsorption from the DCT Stimulates K+ secretion from the DCT

Drugs that alter urinary volume Anything that changes transport systems, permeability or tubular flow rate wil change urinevolume

Diuretics  Osmotic  Thiazides - hydrochorthiazide   Potassium sparing - spironolactoneLoop diuretics – furosemide  ADH levels  ACE inhibitors How do these drugs get to the nephrons luminal cells Delivery of diuretics (except for osmotic diuretics) is via the peritubular capillary beds. They are secreted into the tubule via anion and cation channels, mostly to the PCT They remain free in the filtrate until they bind to downstream receptors. Each binds to a different receptor When multiple diuretics are used, thy will usually act on different regions of the tubule

Exocrine secretion Occurs to enable the elimination of excess ions, toxins and drugs from the blood  Urea  H+  Drugs – penicillin, cocaine, THC

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