L13 Flashcards
What are 2 direct vasodilator drugs
Hydralazine
Minoxidil
When do you use hydralizine
HFail
Acute, severe HTN
What drugs must you combine these direct vasodilators with?
Diuretic = combat ↑renin
BB (sympatholytic) = stop reflex tachycardia
SE of hydralazine
Lupus-like syndrome
Esp for pts with liver disease aka “slow acetylators” since hydralazine inactivated in liver
Where is minoxidil activated?
Liver via sulfonation
How do direct vasodilators vasodilate?
Hydralazine = ↑cGMP Minoxidil = open Katp channels
Net effect of vasodilators
↓afterload
What is pseudo-tolerance in relation to direct vasodilators?
Get temp ↓BP
BP rebounds due to sympa reflex response: ↑HR + ↑renin
What 3 tissues should you remember contain Katp channels? What determines the channel’s tissue specificity?
Heart
Vasc smooth muscle
Pancreatic B cells
Isoform = tissue specificity
Normal fxn Katp channels
Couples metabolic state of cell to its electrical activity
3 drugs that open Katp channels
Minoxidil
Diazoxide
Adenosine
Minoxidil is tissue specific for… + drug use
Vasc smooth muscle - vasodilator to ↓BP
Anti-HTN
Diazoxide is tissue specific for… + drug use
Pancreas - ↓insulin release
Hypoglycemia or hyperinsulinemia
Adenosine is tissue specific for + drug use
Cardiac = A1 receptor = anti-arrhymthic
Vasc smooth muscle = A2 receptor = dilator
Explain Katp channels in heart under ↓ATP
Hypoxia/E depletion = ↓ATP = ↑ADP
Avail adenosine binds A1 receptors
Katp channels open –> hyperpol membrane
NET = shorter AP, ↓contractility
Explain Katp channel in vasc smooth muscle under ↓ATP
Baseline vasc smooth muscle = tonically contracted
↓ATP –> open Katp
↑K+ in, ↓Ca2+ in via voltage Ca2+ channels
Hyperpol –> relaxation = vasodilation
How does adenosine act as vasc smooth muscle?
↓ATP = ↑ADP = ↑adenosine + A2 receptor - helps open Katp channels
What are 2 parts of the Katp channel in pancreatic B cells
SUR1 & Kir 6.2
Explain ↓blood glucose result on Katp channels in pancreas
↓BG –> ↓ATP –> Katp opens –> hyperpol –> ↓insulin release
Where does diazoxide binds the Katp channel in pancreas
SUR1 to open channel
Where does sulfonylurea bind the Katp channel in pancreas - does it open or close the receptor?
SUR1 to close channel
What is the action of ATP and MgADP on the Katp channel in the pancreas? Where does each bind?
ATP closes via Kir 6.2
MgADP opens via SUR 1
How does a gain of function Katp mutation present? Treat
Neonatal diabetes (↓insulin) \+ Sulfonylurea
How does a loss of fxn Katp mutation present? Treat
Neonatal hyperinsulinemia
Diazoxide
What is the cardioprotective mechanism of adenosine & diazoxide
Open cardiac MITOCHONDRIAL Katp channels
What is ischemic pre-conditioning
Post short-term coronary artery occlusion
Change myocyte fxn of tissue affected by occlusion + abnormal wall motion of normal myocardium
After reperfusion during “stunned” period, protected from long duration occlusions that are v damaging
What is the acute phase of ischemic preconditioning
Katp open - including mitochondrial Katp channels
Important to maintain mito fxn
What is the delayed phase of ischemic preconditioning
RISKinases turn on genes for protective proteins –> ↑transcription of these
Which during do you give during ischemic preconditiong, why?
ADENOSINE Binds A1 receptor to help open Katp channels - Mitochondial fxn - ↓HR & contractility Binds A2 - vasodilation
What is ischemic post-conditioning
Short periods of ischemia during reperfusion can be beneficial b/c limit extent of damage
What is remote pre/post conditioning
Transient ischemia of some pt of body (arm)
Liberates an unknown effector
Induces remote cell adaptation to an ischemia that isn’t happening to it - get protection w/o damage
Which drug do you give during stress tests
Adenosine
