Effects of chronic treatment with statins and fenofibrate on rat skeletal muscle: a biochemical, histological and electrophysiological study.
OBJECTIVE
Skeletal muscle injury by hypolipidemic drugs is not fully understood. An extensive analysis of the effect of chronic treatment with fluvastatin (5 mgkg(-1) and 20 mgkg(-1)), atorvastatin (10 mgkg(-1)) and fenofibrate (60 mgkg(-1)) on rat skeletal muscle was undertaken.


METHODS
Myoglobinemia as sign of muscle damage was measured by enzymatic assay. Histological and immunohistochemical techniques were used to estimate muscle integrity and the presence of aquaporin-4, a protein controlling water homeostasis. Electrophysiological evaluation of muscle Cl(-) conductance (gCl) and mechanical threshold (MT) for contraction, index of intracellular calcium homeostasis, was performed by the two-intracellular microelectrodes technique.


RESULTS
Fluvastatin (20 mgkg(-1)) increased myoglobinemia. The lower dose of fluvastatin did not modify myoglobinemia, but reduced urinary electrolytes, suggesting direct effects on renal function. Atorvastatin also increased myoglobinemia, with slight effects on urinary parameters. No treatment caused any histological damage to muscle or modification in the number of fibres expressing aquaporin-4. Either fluvastatin (at both doses) or atorvastatin reduced sarcolemma gCl and changed MT. Both statins produced slight effects on total cholesterol, suggesting that the observed modifications occur independently of HMGCoA-reductase inhibition. Fenofibrate increased myoglobinemia and decreased muscle gCl, whereas it did not change the MT, suggesting a different mechanism of action from the statins.


CONCLUSIONS
This study identifies muscle gCl and MT as early targets of drugs action that may contribute to milder symptoms of myotoxicity, such as muscle cramps, while the increase of myoglobinemia is a later phenomenon.
Pierno
S
S
Department of Pharmacobiology, Section of Pharmacology, Faculty of Pharmacy, University of Bari, Bari, Italy.
Didonna
M P
MP
Cippone
V
V
De Luca
A
A
Pisoni
M
M
Frigeri
A
A
Nicchia
G P
GP
Svelto
M
M
Chiesa
G
G
Sirtori
C
C
Scanziani
E
E
Rizzo
C
C
De Vito
D
D
Conte Camerino
D
D
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D051401:Aquaporin 4 / Q000032:analysis; D000069059:Atorvastatin; D001835:Body Weight / Q000187:drug effects; D018118:Chloride Channels / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004435:Eating / Q000187:drug effects; D005229:Fatty Acids, Monounsaturated / Q000633:toxicity; D011345:Fenofibrate / Q000633:toxicity*; D000077340:Fluvastatin; D006538:Heptanoic Acids / Q000633:toxicity; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000633:toxicity*; D000960:Hypolipidemic Agents / Q000633:toxicity*; D007211:Indoles / Q000633:toxicity; D007674:Kidney Diseases / Q000139:chemically induced; D008055:Lipids / Q000097:blood; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects; D018656:Muscle Fibers, Fast-Twitch / Q000737:chemistry / Q000187:drug effects* / Q000473:pathology; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000473:pathology / Q000503:physiopathology; D009135:Muscular Diseases / Q000139:chemically induced; D018995:Myosin Heavy Chains / Q000032:analysis; D009929:Organ Size / Q000187:drug effects; D011758:Pyrroles / Q000633:toxicity; D051381:Rats; D017208:Rats, Wistar; D012206:Rhabdomyolysis / Q000139:chemically induced; D013997:Time Factors
C496032:Aqp4 protein, rat; D051401:Aquaporin 4; D018118:Chloride Channels; D005229:Fatty Acids, Monounsaturated; D006538:Heptanoic Acids; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D000960:Hypolipidemic Agents; D007211:Indoles; D008055:Lipids; D011758:Pyrroles; D000077340:Fluvastatin; D000069059:Atorvastatin; D018995:Myosin Heavy Chains; D011345:Fenofibrate