Aging and muscle fiber type alter K+ channel contributions to the myogenic response in skeletal muscle arterioles.
Aging diminishes myogenic tone in arterioles from skeletal muscle. Recent evidence indicates that both large-conductance Ca2+-activated (BKCa) and voltage-dependent (KV) K+ channels mediate negative feedback control of the myogenic response. Thus we tested the hypothesis that aging increases the contributions of KV and BKCa channels to myogenic regulation of vascular tone. Because myogenic responsiveness differs between oxidative and glycolytic muscles, we predicted that KV and BKCa channel contributions to myogenic responsiveness vary with fiber type. Myogenic responses of first-order arterioles from the gastrocnemius and soleus muscles of 4- and 24-mo-old Fischer 344 rats were evaluated in the presence and absence of 4-aminopyridine (5 mM) or iberiotoxin (30 nM), inhibitors of KV and BKCa, respectively. 4-Aminopyridine enhanced myogenic tone with aging and normalized age-related differences in both muscle types. By contrast, iberiotoxin eliminated age-related differences in soleus arterioles and had no effect in gastrocnemius vessels. KV1.5 is an integral component of KV channels in vascular smooth muscle; therefore, we determined the relative protein expression of KV1.5, as well as BKCa, in soleus and gastrocnemius arterioles. Immunoblot analysis revealed no differences in KV1.5 protein with aging or between variant fiber types, whereas BKCa protein levels declined with age in arterioles from both muscle groups. Collectively, these results suggest that the contribution of BKCa to myogenic regulation of vascular tone changes with age in soleus muscle arterioles, whereas increased KV channel expression and negative feedback regulation of myogenic tone increases with advancing age in arterioles from both oxidative and glycolytic muscles.
Kang
Lori S
LS
Department of Physiology and Pharmacology, West Virginia University School of Medicine, Morgantown, WV, USA.
Kim
SeJeong
S
Dominguez
James M
JM
Sindler
Amy L
AL
Dick
Gregory M
GM
Muller-Delp
Judy M
JM
D000367:Age Factors; D000375:Aging / Q000378:metabolism*; D000818:Animals; D001160:Arterioles / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D025461:Feedback, Physiological; D006019:Glycolysis; D066298:In Vitro Techniques; D051666:Kv1.5 Potassium Channel / Q000037:antagonists & inhibitors / Q000378:metabolism; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D010084:Oxidation-Reduction; D011188:Potassium / Q000378:metabolism*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D024642:Potassium Channels, Voltage-Gated / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D011916:Rats, Inbred F344; D014661:Vasoconstriction / Q000187:drug effects
C496983:Kcna5 protein, rat; D051666:Kv1.5 Potassium Channel; D051036:Large-Conductance Calcium-Activated Potassium Channels; D026902:Potassium Channel Blockers; D024642:Potassium Channels, Voltage-Gated; D011188:Potassium