K+ and Ca++ regulation Flashcards
Two primary functions of K+:
- cell metabolism
2. ratio of intra/extracellular K+ creates cell resting membrane potential
% of total body K+ stored intracellularly?
98%
Total body stores of K+:
3,000-4,000 mM
50-55 mM/kg
Two main factors regulating Na-K-ATPase to get K+ back into the cell:
- insulin
2. catecholamines
Three main ideas with insulin K+ regulation:
- increases activity of Na-K-ATPase
- Promotes skeletal muscle uptake
- eating –> inc insulin –> prevents sharp rise in serum K+
How does exercise affect K+ in serum?
Muscle cells release K+ –> proportional to degree of exercise
How does serum pH affect K+?
H+ uses up bicarb in serum
To balance charge, K+ leaves cell
Acute treatment for acidotic patient with hyperkalemia:
Insulin
glucose
Ca++ (to stabilize cardiac myocytes)
% of total body K+ handled by principal cells (late distal tubule and cortical collecting duct):
10%
Two principal cell channels facilitating excretion of K+:
ROMK
BK
Aldosterone action with respect to K+:
Directly stimulated by high K+
Upregulates ROMK
Stimulates Na-K-ATPase
What does Angiotensin II do to ROMK?
Inhibits
What can block ROMK to help retain intracellular K+?
Mg++
When is BK active?
High K+ diet
What is the function of the a-intercalated cell in the distal convoluted tubule/collecting duct?
reabsorption of K+
