Lec 11 - Human growth Flashcards
when is max rate of growth
fetus
about 70cm/year
what cell behaviours are affected by growth hormone and IGF-1
- survival (ie prevent or trigger apoptosis)
- hypertrophy
- proliferation
- differentiation
- metabolism
what does hypothal release
ghrh
what type of cell in the APG has the GHRH receptor
somatotrophs
what type of receptor is GHRH receptor
Gs GPCR
activates adenylyl cyclase = cAMP = activation of PKA
what tissues does GH directly act on
- bone
- adipose tissue
- muscle
- liver
where is igf1 produced
in liver mostly (can be in bone)
in response to GH stimulation
where does igf act
- adipose tissue
muscle
etc.
= endorcrine effects - but also bone
= paracrine effects
GH gene
cluster of 5 closely related genes
GH-N = gh normal gene ie the one in circulation
(homology in between species as well)
whivh gh gene expressed in plactena
GH-V
GH-N codes for 2 different variations of GH, what are they
22kDa = the predominant one
20kDa (some residues deleted) = not sure what this one does
Gh produced as a precursor protein, what is cleaved when it gets secreted
n-terminal signal peptide
why would serial sampling be needed to take GH levels
secreted in pulses
and mostly at night
diff between struc of igf1 and gh
igf1 a much smaller peptide than gh
what are the 5 zones in bone
- reserve zone
- proliferative zone
- maturation zone
- hypertrophic zone
- invasion zone
what does reserve zone contain
progenitor cells sat in matrix of collagen
provide cells that feed into next layers
what does proliferative zone contain
chondroblasts organised into columns
what does maturation zone contain
the chondroblasts turn into chondrocytes
these secrete a matrix that forms scaffold for formation of trabecular bone
what does hypertrophic zone
the cells grow in size duh
which then undergo apoptosis
which leave behind lacunae
what does invasion zone contain
osteoblasts come up and deposit bone onto the scaffold left behind by chondrocytes
which zones does gh and igf1 act on
all except invasion zone
what 3 things does GH stimulate in terms of metabolsim
- lipolysis
- amino acid uptake and protein synth
- glucose output from liver
what 3 things does IGF1 stimulate in terms of metbaolism
- lipogenesis
- amino acid uptake and protein synth
- uptake of glucose (similar to insulin)
diff between gh and igf in terms of the receptors
gh receptor has to recruit an enzyme to the recpetor once bound
igf already has catalyitc activity built into the receptor
