Brown adipocytes isolated from warm acclimated guinea pig do not respond to noradrenaline (NA) in spite of their marked thermogenic response in vivo. In contrast, in cold-acclimated guinea pigs, isolated brown adipocytes show substantial increase in capacity for a thermogenic response to NA. Chronic stimulation with a β3-AR agonist increased insulin-sensitivity of brown adipose tissue (BAT) in the guinea pig. To investigate the responsiveness of glucose transport to insulin, to NA, and to β3-AR agonists, we used BAT of guinea pigs as an animal known to be insulin-resistant. Results of this study showed that no β3-adrenergic agonist used, such as CL 316,243, BRL 37344, was able to stimulate oxygen uptake in BAT cells from cold-acclimated or new born guinea pigs. However, noradrenaline (NA), adrenaline (A) and isoproterenol (ISO) had a marked thermogenic effect on these cells. In contrast, in a comparative study in warm-acclimated rat BAT cells, CL 316,243 was even more potent than NA in stimulating oxygen uptake. We concluded that guinea pigs lack β3-ARs in their BAT. These results were interesting and noteworthy, suggesting that guinea pigs can be a natural model for β3-ARs knockout.
Key words: Brown adipose tissue (BAT), White adipose tissue (WAT), β3-ARs, guinea pig.
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