Vasodilators Flashcards
why does increasing K+ channel opening relax vascular smooth muscle
K+ flux sets the membrane potential
the longer the K+ channels are open, the closer the membrane potential is to K+ equilibrium potential
the closer the membrane potential is to the K+ equilibrium potential, the harder it is to depolarize the membrane enough to open voltage gated Ca2+ channels
drugs that are K+ channel agonists/openers
Minoxidil
Diazoxide
Adenosine
minoxidil metabolism
prodrug
activated in vivo by sulfotransferase 1A1
what is minoxidil used with
with loop diuretics and beta blockers
effects of minoxidil
very potent vasodilator - effective in severe, drug resistant forms of htn
what may contribute to minoxidil efficacy
cAMP PDE inhibition
minoxidil structure
diazoxide indication
used IV to tx acute htn
effects of diazoxide
very potent vasodilator - effective in severe, drug resistant forms of htn
diazoxide moa
inhibits release of insulin from pancreatic beta cells
diazoxide structure
what does adenosine bind to
A1 receptor- a GPCR
what does adenosine do
increases conductance of a K+ channel
what is adenosine used for
supraventricular arrhythmias
coronary stress test
where is the nitric oxide synthase
vascular endothelium
where does NO diffuse to
vascular smooth muscle
what is found in vascular smooth muscle
guanylate cyclase
how can NO directly relax smooth muscle
by being exogenously applied
where does NO bind and then what does it do
NO binds to heme iron prosthetic group in guanylate cyclase, stimulating production of cGMP and activating protein kinase G (cGKI)
how does protein kinase G relax smooth muscle
inhibition of L-type Ca2+ channels (Cav1.2)
stimulation of Ca2+ activated K channels (BKca)
decreased MLC phosphorylation (myosin phosphatase 1)
enhanced Ca2+ uptake in to ER (phospholamban)
what are features of organic nitrates
non-selective vasodilators
breakdown to NO
don’t require functional endothelium
acute or chronic admin
types of organic nitrates/nitrites
organic nitrates PK
organic nitrates indications
given sublingually in tx of acute angina attacks
given orally or transdermally for prolonged prophylaxis
tolerance occurs with continuous admin
pharmacogenetics of glycerol trinitrate
glu 504 Lys polymorphism in ALDH-2
glu 504 is 10x more efficient in metabolizing GTN
what likely accounts for lack of efficacy of GTN in large % of asian pop
30-50% of asian pop has at least one Lys 504 allele
what is the diff in activation of GTN and ISMN/ISDN
ISMN and ISDN activation is ALDH-2 independent
what is the mechanism of cell damage initiated by hyperglycemia
AGE precursor methylglyoxal inhibits vasorelaxation stimulated by acetylcholine/NO
sodium nitroprusside (SNP) indication
given IV for acute management of hypertensive crisis and severe decompensated hf
SNP effects
dilates veins and arterioles
SNP metabolism
metabolized in erythrocytes to NO, 4CN-, and cyanmethemoglobin
hydralazine effects
dilates arterioles preferentially
hydralazine moa
moa not clear
appears to interfere with release of Ca from the ER
may also prevent oxidation of NO