Proteins and Nitrogen Containing Compounds (7.1-1.16)

General metabolism of proteins

absorption starts in small intestine, filtered by kidneys, reabsorbed in proximal convoluted tubule and loop of Henle

Site for synthesizing plasma proteins

most are synthesized in liver except hemoglobin and peptide hormones

primary function of plasma proteins

maintain oncotic pressure, transport nutrients, blood clotting

protein electrophoresis

e- carry proteins across a field depending on size and charge

7.4 and 7.5

na

elevated urine of albumin

Diabetes, Hypertension, Kidney damage, and heart failure

elevated urine in immunoglobulin

multiple myeloma and infections

elevated urine in microalbumin

diabetes, hypertension, cardiovascular disease

elevated urine in B2 microalbumin

tubular disorders in kidneys

multiple myeloma

rogue cancer cells mass produce immunoglobulins, decreasing alpha2 macroglobulins and increasing beta2 microglobulins

nephrotic syndrome

increase in beta2 macroblobulins and decrease in overall protein levels and decrease in overall oncotic pressure

liver disease

proteins decrease, low AG ratio and coagulopathies

coagulopathies

no coagulation, causes bleeding, causes ascites

hypoproteinemia

nephrotic cause, oncotic pressure in peritoneal cavity > oncotic pressure in blood

ascites

a giveaway for hypoproteinemia, excess water in peritoneal cavity

acute phase reaction

increase in both alphas, but alpha2 is more noticeable

biuret method

usual method for protein testing, Cu2+ ions interact with peptide bonds to detect them

Biuret reagents

NaOH for alkalinity, NaK tartrate, K iodide, CuSo4

coomassie brilliant blue method

uses refractometry where the refractive index of a solution is proportional to protein concentration, dye binds to protein, increasing absorbance and 595nm

bromresol green method

binding with anionic dyes to get a high pka, very small sample size makes it difficult to get controls in range (3.5-5 g/dL)

gel chromatography

separation on differential affinity between liquid phase migrating up gel plate and gel itself

ultracentrifugation

spin very fast to separate proteins

maple syrup urine disease MSUD

enzymatic deficiency, can’t break down branched amino chains

MSUD deficient

BCKDC branched chain keto acid dehydrogenase complex

essential branched chain amino acids BCAA

leucine, isoleucine, valine

alkaptonuria

deficient in homogentistic acid oxidase (HGA) leading to build up and ochronosis

ochochronosis

symptom of alkaptonuria, darkening of body tissues due to HGA “black diapers”

phenylketonuria PKU

can’t metabolize phenylalanine, musty urine odor, brain damage, can be fixed with pku free diet

cystinuria

not metabolic/enzymatic deficient, defect in the AA transport system itself in kidney, result in kidney stones

can’t be absorbed in cystineuria

divalent aa, cystine, lysine, arginine, ornithine

Urea N % in NPN

45%

Uric Acid % in NPN

20%

creatinine % in NPN

5%

ammonia % in NPN

0.2 %

urea assessment

dehydration and will increase if kidneys aren’t perfused with blood

Fearon reaction

urea + diacetyl +hot acid bath = diazine + color change to see spectrophotomatically

prerenal azotemia

less blood makes it to kidneys, usually by dehydration and impaired blood flow or high protein catabolism

BUN

blood urea nitrogen

renal azotemia

acute renal failure, there is a problem in the kidney itself

BUN:Cr ratio

10:1-20:1, only valid if both BUN and Cr are out of range, helps distinguish azotemia types

postrenal azotemia

normal BUN:Cr but decrease GFR, congestive heart failure, dehydration, obstructive renal cell carcinoma

creatinine measurement

imperfect measurement of glomerular filtration rate and renal function, only high Cr is significant,

creatinine synthesis

related to muscle mass, more muscle mass means more Cr production

creatinine excretion

excreted through the kidneys, great for gfr measurement as its nearly entirely filtered through the glomerulus

what throws off gfr measurements in creatinine

its also slightly secreted in the distal convoluted tubule

creatinine excretion in renal disease

excretion decreases

renal disease on creatinine conc

because Cr is excreted by kidneys, decrease in renal function increases Cr concentration

jaffe method

Cr and picnic acid (explosive) in alkaline solution

interferes with the jaffa reaction

protein, glucose, uric acid, ascorbic acid, acetone, keto acids, cephalosporins

creatinine ranges in men and women

men 0.9-1.2 mg/dL and women 0.6-1.1 mg/dL

women are lower because they typoically have less muscles

uric acid shows

gout, lesch-nyhan syndrome, cytotoxic chemotherapy, malignancies

uric acid synthesis

break down purines, A and G, catabolized to xanthine then oxidased to uric acid, comes from diet and cell/DNA breakdown

uric acid excretion

most excreted in kidneys, rest by GI tract

gout

monosodium urate crystals cause inflammation in peripheral joints

podagra

gout in the big toe

gout and pseudogout

crystals parallel to light are yellow in gout, blue when parallel is psuedogout

uricase method

common enzymatic method of uric acid with uricase to make allantoin with H2O2 and CO2 then beroxidase to make chromogen

gout affect uric acid levels

increases uric acid levels

urea lab results

indicates kidney issues, low levels see malnutrition and liver disease

uric acid lab results

high levels indicate gout or disorders, low levels kidney disorders and genetic disorders affecting its metabolism

creatinine lab results

high levels indicate kidney issues, more specific indicator as its less effected by things like diet

ammonia lab results

high levels indicate liver issues or disorders affecting its metabolism

what is the routine method for protein identification and quantification

Biuret method, Cu2+ binds to peptide bonds and creates purple at 540nm

How to calculate BUN concentration from urea concentration

divide urea concentration by 2.14, to find urea concentration multiply BUN by 2.14

Cr ranges in most labs

0.6-1.1mg/dL