Whole Body biochemistry Flashcards
What hormones are the primary regulators of calcium levels. What else do they affect?
Calcitonin - produced by the thyroid –> promotes Ca incorporation into the bone (increases osteoblast & decreases osteoclast activity), inihibits renal & intestinal reabsorption of Ca –> decreased blood Ca levels. (like PTH, also inhibits P renal absorption)
PTH - produced by the parathyroid gland, results in increased Ca blood levels and decreased P levels. Stimulates
- Re-absorption by kidneys (& excretion of P)
- Production of calcitriol by prox. tubules –> re-absorption of Ca & P from intestines
- Increased bone turnover & release of Ca
PTH-rp (related protein)
- normally a fetal hormone for Ca balance
- ay be aberrently produced by some tumors in an adult, causing PTH-like effects –> hyper-calcemia
What hormones regulate sodium blood levels? What secretes them and what are their full effects?
Aldosterone –> produced by adrenal cortex
- stimulates re-absorption of Na & excretion of K from distal tubules
- Major regulator of blood volume
- Disorders of the adrenal cortex (cushings or addisons) can show up as abnormal Na & K levels
Where does most of potassium in the body reside? What affects its shifting between body fluid compartments?
Are K serum levels good indicators of total body K?
What about if K serum levels are low?
Found mostly in the ICF
Changes in acid-base balance affects shifts in K
acidemia –> will shift to plasma space to help counter this
alkalosis –> more will shift into the ICF
K serum levels do not tell us how much is present, as most is present inside cells
However, a low serum K indicates that most of the body is depleted of K –> this is life threatening and needs to be addressed!
As well, acid-base balance disorders may mask a hypokalemic state, be careful when treating
(if you treat with an alkalinizing fluid, K will shift intracellularly, and there will be none available for heart contraction –> death)
Total serum calcium includes ionized & albumin-bound calcium. Ionized calcium can also be measured, and measures only the physiologically important calcium. Why would we choose to measure ionized calcium?
- Corroborate a hypocalcemia that is due to hypo-albunemia
- Corroborate hyper-parathyroidism as the cause of hypercalcemia (tumour not found)
Is magnesium regulated by hormones?
Is serum magnesium a good indicator of total Mg?
No - absorption does occur via intestine & kidneys though. No
What are grass staggers?
Cows put out on pasture in early spring. Plants are low in magnesium –> cows are low in magnesium, and display ataxia, falling over, and twitching ears
Can hemolytic anemia & hyperphosphatemia be related?
Yes - lots of P in RBCs
What organs produce lipoproteins? Where does lipolysis occur? What regulates lipoprotein lipase? Name two mechanisms by which diabetes mellitus causes lipidemia what organ clears lipoprotein?
Small intestine, liver (liver produces most of cholesterol)
Surface of endothelial cells
Insulin –> diabetes mellitus can cause lipidemia by
a. decreased lipolysis
b. decreased stimulation of lipoprotein binding to cellular receptors –> decreased clearance by liver
Liver
What is cholesterol used for in the body?
- Repair of cells, formation of new ones
- To produce steroids
- Bile acid production
What affects lipoprotein levels?
- Amount of production
- Amount degraded by lipolysis
- Altered clearance or cellular uptake
What affects does lipemia have on measured TP by refractometry, and RBCs?
- Causes elevated TP based on refractometry
- Increases amount of hemolysis
Are triglycerides & cholesterol mostly free/unbound in the serum?
No - not soluble in blood. Most are bound by protein –> hence lipoprotein
What are the causes of elevated cholesterol?
- Cushings –> excess production of steroids
- Cholestasis –> altered clearance in bile, and build-up of bile acids, which is comprised of cholesterol, increased production
- Post-prandial –> increased production by enterocytes
- Protein-losing nephropathies –> increased production and decreased lipolysis
- Diabetes mellitus –> decreased lipolysis b.c. of lack of (or lack of response to) insulin, major regulator of lipoprotein lipase and uptake by cells (altered lipolysis & clearance or uptake)
- Pancreatitis
- Hypothyroidism
- Idiopathic in miniature schnauzers
What causes hypocholesterolemia?
- Liver disease that causes decrease in functional mass, decreased production
- Portosystemic shunt (some), decreased production
- Addison’s, unknown
- Protein-losing enteropathy, increased loss
In a cow, elevated non-esterified fatty acids indicate what?
Negative energy balance
increased with stress, fatty liver, ketosis
