Intracellular potassium and membrane potential in rat muscles during malnutrition and subsequent refeeding.
Nutrition alters total body potassium (TBK) and muscle potassium but little is known about in vivo intracellular K+. We measured free intracellular potassium-ion activity (aKi+), membrane potential (Em), and total potassium (Kt) and calculated intracellular potassium concentration [K+]i in predominantly slow- (soleus) and fast- (extensor digitorum longus) twitch muscles in rats undergoing underfeeding and subsequent refeeding. After underfeeding, aKi+ and Em decreased (P less than 0.025 and P less than 0.006, respectively) only in soleus muscle with restoration after refeeding, whereas [K+]i decreased in both muscles (P less than 0.005) and remained low after refeeding. K+ supplementation did not significantly change these indices or the ratio of free to total intracellular potassium (gamma Ki+). The data show that aKi+ behaves differently from [K+]i during malnutrition and that changes in aKi+ occur especially in slow-twitch fibers, suggesting that previously observed changes in TBK and muscle function are the result of fundamental alterations in muscle-cell energetics and membrane functions, not just mass.
Pichard
C
C
Division de Gastroenterologie et Nutrition, Hopital Cantonal Universitaire de Genève.
Hoshino
E
E
Allard
J P
JP
Charlton
M P
MP
Atwood
H L
HL
Jeejeebhoy
K N
KN
D000818:Animals; D001835:Body Weight; D005247:Feeding Behavior; D007425:Intracellular Membranes / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism; D008297:Male; D008564:Membrane Potentials; D009132:Muscles / Q000378:metabolism* / Q000473:pathology / Q000502:physiology; D009748:Nutrition Disorders / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D009929:Organ Size; D010758:Phosphorus / Q000378:metabolism; D011188:Potassium / Q000378:metabolism* / Q000494:pharmacology; D051381:Rats
D010758:Phosphorus; D008274:Magnesium; D011188:Potassium