L35. Kidney (1) Flashcards
(12 cards)
Using the example of a salivary gland, tell me about secretory epithelia?
- Acinar cells of the salivary gland represent a leaky secretory epithelium
- Produces an isotonic primary fluid (containing ions and water) that flows into the mouth
- Other examples: sweat glands, lacrimal (tear) duct, stomach, small intestine, pancreas
What is chloride secretion in secretory epithelia?
- Na+/K+-ATPase generates a low sodium concentration inside the cell that can be used by transporters or channels on the apical side, AND also on the basolateral side
- Na+/K+-ATPase - active transport of Na+ out of cell generates gradient for Na+ to enter the cell from basolateral side
- Na+/K+/2Cl- enter the cell through the co-transporter (NKCC1, basolateral) to facilitate secretion of Na+, K+, and 2Cl-
- Chloride is secreted apically via a chloride channel
- Sodium is absorbed on the basolateral side by the Na+/K+-ATPase
- Potassium is absorbed by a basolateral K+ channel
What is sodium secretion in secretory epithelia?
- Apical chloride secretion results in a negatively charged lumen and a positively charged interstitium driving paracellular sodium secretion in a leaky epithelium
- Water will follow down its osmotic gradient
What is water secretion in secretory epithelia?
- Movement of ions makes the basolateral side hypotonic and leads to water secretion both trans and paracellularly
- Water severely decreased if the chloride channel is defective e.g. genetic changes in the CFTR/cystic fibrosis gene
Give a comparison of leaky and tight epithelia?
Leaky epithelia e.g. PCT of kidney
- Na+ coupled solute transport e.g. SGLT1
- High rates of Na+ re-absorption (bulk absorption)
- High water permeability (trans and paracellular)
Tight epithelia e.g. CCT of kidney
- Na+ channel (ENaC)
- Low rates of Na+ re-absorption for fine-tuning
- Low water permeability (only transcellular, AQP2)
Tell me about hormonal regulation of renal epithelia by AVP/vasopressin/ADH?
- The PCT, PST, and tDLH are leaky (water permeable)
- The tALH up to CNT are tight (water impermeable)
- The CCT, OMCD, and IMCD are tight epithelia (water permeability is facilitated by vasopressin (AVP/ADH)
What are some functions of the kidney?
- Water homeostasis (hydration, blood pressure)
- Reabsorption of nutrients (glucose, amino acids)
- Salt/ion homeostasis (Na+, K+, Ca2+, blood pressure)
- Excretion drugs
- pH-regulation
- Gluconeogenesis
- Metabolism
- Hormone production erythropoietin
What do you expect of normal urine to contain?
- Water (1.5/L/day)
- 95-98% of urine is water
- Creatinine
- Urea
- H+, NH3 (ammonia)
- Na+, K+
- Drugs (anti-viral, diuretics)
What is the colour scale of urine for?
Colour scale to estimate total body water of athletes: yellow colour is pigments from breakdown of haemoglobin
- Above the bar = you have been drinking enough water if urine is clear to pale yellow in colour
- Below the bar = you need to drink water
Athletes can be tested with a refractometer to measure specific gravity (equivalent to osmolarity of the urine)
What do you expect of pathological/abnormal urine to contain?
- Glucose (glucosuria, diabetes)
- Protein (proteinuria)
- Blood (erythrocytes, haematuria)
- Haemoglobin (haemoglobinuria)
- Leucocytes
- Bacteria (infection)
What should normal urine look, taste, and smell like?
Look:
- Clear, light, or dark amber look
Taste:
- Acidic (pH:5-6), NOT sweet
- pH dependent on diet
* Veggies: pH up to 7.2
* Meat eaters (high protein): pH 4.8
Smell:
- Unremarkable
What should pathological/abnormal urine look, taste, and smell like?
Look:
- Golden, red, brown, blue
Taste:
- Sweet: diabetes mellitus
Smell:
- Like fruit: ketosis (fasting), diabetes, chronic alcohol abuse
- Rotten: infection (bacteria), tumour
