23: hormonal signaling in mammals (part 2)

Question 1

what is a radioimmunoassay?

Answer 1

a way to quantify hormones. Add radio labeled hormone to bound antibodies that recognizes the hormone. Then add varying amounts of unlabeled hormone (keeping the radiolabled hormone constant). Plot the data in a standard curve with ratio of bound/unbound hormone on y axis and unlabeled hormone added on x axis. Can use to determine how much unlabeled hormone is in a patient based on the radiolabeled ratio of bound/unbound.
23 slide 3

Question 2

describe ELISA

Answer 2

enzyme linked immunosorbent assay. used to quanitfy hormones without radioisotopes, its basically a fancy Western. Add antibodies that bind to the hormone and conjugate with an enzyme (instead of a fluorescence) which will tell you how much is there. can be direct, indirect, sandwich, or competitive. Very common test used in lots of things like virus or cancer screenings, pregnancy tests, food allergen tests

Question 3

how do hormones interact with their receptors? (intra or extra cellular?)

Answer 3

Both intracellular and extracellular interaction occurs. Water soluble peptide and amine hormones act extracellularly, the alter existing enzymes and have a fast response. Water insoluble hormones act intracellularly and alter transcription levels, causing a slow acting response

Question 4

name the classes of hormones and whether they are fast or slow acting

Answer 4

fast: peptide, catecholamine, eicosanoid
slow: steroid, vitamin D, retinoid, thyroid
nitric oxide (cytosolic receptor and second messenger)

Question 5

describe peptide hormones and examples

Answer 5

composed of amino kids (3-200) and encoded in the genome. Often they are translated as much larger polypeptides (pro hormones) that are cleaved into mature hormones, often modified. concentration of peptide hormones in secretory granules can be so high its crystalline
Act through surface receptors
ex: insulin, glucagon, calcitonin

Question 6

describe insulin secretion in response to high blood glucose in pancreatic B cells

Answer 6

GLUT2 allows glucose to transport into the B cell. hexokinase IV (glucokinase) converts to glucose-6-phosphate which keeps glucose concentration low so it flow into the cell. glucose-6-phosphate goes through glycolysis, the CAC, and oxidative phosphorylation, producing ATP. ATP inhibits the ATP-gated K+ channel and leads to depolarization as K+ stops flowing out of cell. Depolarization triggers voltage-gated Ca2+ channel to open. Ca2+ influx promotes release of insulin granules which travel in the bloodstream to other cells and trigger insulin responses

Question 7

what is diabetes mellitus?

Answer 7

a defect in insulin production or action.
type I is due to a small number of pancreatic B cells, therefore only small amount of insulin is produced. can be treated by insulin injections
type II is when the insulin signal is not transduced correctly. harder to treat, cannot be helped by insulin injection because the problem is with the receptors.

Question 8

how much do peptide hormones vary in structures?

Answer 8

it is possible for very similar structures to have vastly different responses. one example is human oxytocin and vasopressin which differ by only 2 amino acids but cause totally different responses (uterine contractions and water absorption in kidneys)

Question 9

describe catecholamine hormones. how are they synthesized? examples?

Answer 9

they have a catechol ringed structure (know this structure, a benzene with two OH groups on C1 and C2). synthesized from tyrosine. some function as neurotransmitters. they are stored in high concentrations in vesicles
Act through surface receptors.
ex: dopamine, norepinephrine, epinephrine (can all be made in one biosynthetic chain)

Question 10

describe Eicosanoid hormones. how are they synthesized? examples

Answer 10

derived form arachidonate (from phospholipids) and mostly make prostaglandins, thromboxanes, and leukotrienes. All are important molecules for pain, inflammation, clotting, and anaphylaxis. They are paracrine hormones and are NOT stored, only made as needed!
Act through surface receptors
ex: prostaglandins, thromboxanes

Question 11

describe steroid hormones. how synthesized? examples

Answer 11

derived from cholesterol. carried through bloodstream (bound to carrier proteins bc hydrophobic). 2 types are glucocorticoids and androgens.
Act through nuclear receptors
ex: cortisol (glucocorticoid) and testosterone (androgen)

Question 12

describe vitamin D hormone. how synthesized?

Answer 12

derived from diet or light induced degradation of 7-dehydrocholesterol (forms vitamin D3, then 25-hydroxycholecaldiferol, then Calcitriol). Calcitriol works with parathyroid hormone to maintain Ca2+ levels.
Acts through nuclear receptor (activates transcription of protein needed to bind Ca2+)

Question 13

describe retinoid hormones. how synthesized?

Answer 13

derived from B-carotene in liver which makes Vitamin A (retinol), a prohormone. In many tissues vitamin A is made into the hormone retinoic acid. Receptors are located in almost ALL tissues
Act through nuclear receptors

Question 14

describe thyroid hormones. how synthesized?

Answer 14

derived from thyroglobulin (pro hormone) which the thyroid gland iodinates the Try residues. Then proteolysis makes thyroxine (T4) or triiodothyronine (T3). This is really a peptide hormone, but is just an unusual one bc is acts through nuclear receptor.
see slide 20 for T3 and T4 structures. T4 has 4 I’s total and T3 has 3 I’s total.

Question 15

describe nitric oxide as a “hormone”. how synthesized?

Answer 15

derived form arginine via nitric oxide synthase. it functions in blood vessels by CaM activating NOS and promoting NO synthesis. NO interacts with soluble guanylate cyclase and makes cGMP increase.