Ca2+ and lipolysis in adipocytes from exercise-trained rats.
The effects of Ca2+ on lipolysis and protein kinase activity in adipocytes from exercise-trained rats were investigated. Chronic exercise significantly increased lipolytic responses to norepinephrine and dibutyryl adenosine 3',5'-cyclic monophosphate (cAMP). The inhibitory effects of N-(6-aminohexyl)-5-chloro-1-naphthalene sulfonamide (W-7), a calumodulin inhibitor, on norepinephrine- and dibutyryl cAMP-stimulated lipolysis were significantly greater in trained than in sedentary rats. Training did not alter cAMP-dependent protein kinase activity. However, the inhibitory effect of W-7 on cAMP-dependent protein kinase activity was much greater in trained than in sedentary rats. The basal intracellular free Ca2+ concentration ([Ca2+]i) was significantly higher in trained than in sedentary rats. The rapid and transient increases in [Ca2+]i due to adrenocorticotropic hormone and phenylephrine from basal levels were significantly lower in trained than in sedentary rats. However, the higher basal [Ca2+]i level in trained rats led to increases in sustained [Ca2+]i levels after stimulation. We concluded that in trained rats the regulation of protein kinase activity by cAMP depends to a greater degree on Ca(2+)-calmodulin complex than it does in sedentary rats and that training alters adipocyte intracellular Ca2+ homeostasis, including [Ca2+]i responsiveness to hormones.
Izawa
T
T
Department of Health and Sports Sciences, University of Electro-Communications, Tokyo, Japan.
Komabayashi
T
T
D017667:Adipocytes / Q000378:metabolism*; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D008066:Lipolysis / Q000187:drug effects; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D010805:Physical Conditioning, Animal; D051381:Rats; D017208:Rats, Wistar; D013449:Sulfonamides / Q000494:pharmacology
D013449:Sulfonamides; D003994:Bucladesine; C017967:W 7; D017868:Cyclic AMP-Dependent Protein Kinases; D002118:Calcium; D009638:Norepinephrine