Electrolytes and Motility Flashcards
If rehydrating orally, what is required in addition to water and electrolytes?
glucose
b/c electrolytes are only taken up via cotransport mechanisms with glucose
ex: SLGT (sodium-linked glucose transporter)
Tight junctions between enterocytes are regulated by
cytokines, bacterial toxins, hormones
Fluid uptake is primarily mediated by what
NaCl uptake (electroneutral) Na+/H+ exchanger Cl-/bicarb exchanger
Na+, Glc, aa, and bile salt uptake is electrogenic/electroneutral
electrogenic
they are usually coupled with Na+
that means there is an immediate charge imbalance b/c transporter itself does not keep a proper charge balance
Cl- follows to balance charge
What is primary molecule secreted to control water movement into the intestine AND its transporters
Cl-
NKCC1 on basolateral surface
CFTR in crypts on apical surface
Ca2+ absorption steps and regulation
binds intracellular calbindin
basolateral transport via Na+ ATPase or exocytosis
Vit D upregulates Ca2+ channel expression
What regulates Ca2+ uptake at the level of the intestine
Vit D upregulates Ca2+ channel expression
Iron taken up by what transporter
DMT1 (divalent metal transporter 1)
CFTR major intracellular regulatory molecules
cAMP
cGMP
Cholera toxin and diarrhea
cholera toxin: agonist that increases cAMP
high cAMP activates CFTR
CFTR secretes Cl-
secretory diarrhea results
VIPoma
excess VIP –> increase intracellular cAMP
high cAMP activates CFTR
CFTR secretes Cl-
secretory diarrhea results
Linaclotide mechanism
activates guanylate cyclase type C in enterocytes
cGMP activates CFTR
CFTR secretes Cl-
increased intestinal secretions help relieve constipation
Desiccation of stool is mediated primarily by what molecule
Na+
electrogenic and electroneutral mechanisms
Secretory diarrhea is primarily due to
CFTR activation (cAMP or cGMP) infectious or inflammatory processes or VIPoma
Osmotic diarrhea due to
poor absorption of lumenal contents
water pulled from bloodstream via osmosis
