Effects of adenosine and pertussis toxin on lipolysis in adipocytes from exercise-trained male rats.
The sensitivity and responsiveness of adipocyte lipolysis to adenosine and pertussis toxin were studied in exercise-trained male rats. Exercise training (9 weeks of treadmill running) significantly increased lipolytic response of adipocytes to noradrenaline (NA). Addition of adenosine deaminase (ADA) to reaction mixture effectively enhanced NA-stimulated lipolysis in adipocytes from both conditioned rats. However, under these conditions, the difference due to exercise training was still evident, although the difference was less pronounced. The inhibition curves of the R-site adenosine analogue N6-phenylisopropyladenosine (PIA) against "basal" (lipolysis in the presence of ADA) and NA-stimulated lipolysis were almost comparable between two groups. Only a small (approx. 2-fold) increase in IC50 of adipocyte lipolysis was observed in each inhibition curve in exercise-trained rats. Within 120 min of addition of pertussis toxin to adipocytes from control rats, "basal" lipolysis was significantly increased as compared to "basal" lipolysis in the absence of toxin at the same point. Similarly, pertussis toxin significantly increased "basal" lipolysis in exercise-trained adipocytes. However these were relatively sensitive to pertussis toxin, since significant effect of toxin was seen within 60 min. An addition of NA (0.1 uM) to the medium in the presence of ADA and toxin significantly increased adipocyte lipolysis in both conditioned rats. Again, under these conditions, we observed that the maximal rate of lipolysis of adipocytes from exercise-trained rats was increased as compared to control rats. These results suggest that the decreased input through the inhibitory pathway in lipolytic cascade may be not rate limiting for the amplified lipolytic responsiveness of adipocytes to hormonal stimuli in exercise-trained rats.
Shinoda
S
S
Department of Preventive Medicine and Public Health, Tokyo Medical College, Japan.
Izawa
T
T
Komabayashi
T
T
Suda
K
K
Tsuboi
M
M
Iwane
H
H
D000241:Adenosine / Q000494:pharmacology*; D000243:Adenosine Deaminase / Q000378:metabolism; D000244:Adenosine Diphosphate / Q000378:metabolism; D000273:Adipose Tissue / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D066298:In Vitro Techniques; D008066:Lipolysis / Q000187:drug effects*; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D037342:Pertussis Toxin; D010660:Phenylisopropyladenosine / Q000378:metabolism; D010805:Physical Conditioning, Animal; D051381:Rats; D011919:Rats, Inbred Strains; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
D010566:Virulence Factors, Bordetella; D010660:Phenylisopropyladenosine; D000244:Adenosine Diphosphate; D037342:Pertussis Toxin; D000243:Adenosine Deaminase; D000241:Adenosine; D009638:Norepinephrine