Effect of adenosine deaminase, N6-phenylisopropyladenosine and hypothyroidism on the responsiveness of rat brown adipocytes to noradrenaline

Abstract

Adenosine deaminase (1 unit/ml) potentiated the lipolytic action of noradrenaline in adipocytes isolated from brown adipose tissue of 1- and 6-week-old rats by decreasing the EC50 (concn. giving 50% of maximal effect) for noradrenaline by 3-4-fold. With cells from neonatal rabbit tissue, adenosine deaminase only had a small, non-significant, effect on the EC50 for noradrenaline. Lipolysis in rat brown adipocytes was inhibited by low concentrations of N6-phenylisopropyladenosine (PIA). Rabbit cells were far less sensitive to PIA. PIA, prostaglandin E1 and nicotinate all inhibited noradrenaline-stimulated respiration in rat brown adipocytes. Hypothyroidism diminished the maximum response of respiration and lipolysis to noradrenaline in rat cells and increased the EC50 for noradrenaline. Responsiveness of lipolysis to noradrenaline was particularly decreased in hypothyroidism and was partially restored by addition of adenosine deaminase. Lipolysis in cells from hypothyroid rats was more sensitive to the anti-lipolytic action of PIA. Bordetella pertussis toxin increased lipolysis in the presence of PIA, suggesting an involvement of the Ni guanine-nucleotide-binding protein in the control of brown-adipocyte metabolism.

Abstracts from Purines 2014, an International Conference on Nucleotides, Nucleosides and Nucleobases, held in Bonn, Germany, from July 23–27, 2014

“…Additionally, adenosine is critical for the regulation of glucose homeostasis and insulin signaling in mice [9][10][11]. Importantly, similar to findings in WAT, adenosine inhibits lipolysis of hamster and rat brown adipocytes and reduces the sensitivity to catecholamines [12][13][14][15][16]. Besides adipocytes function, there is additional evidence that adenosine receptors regulate adipogenic differentiation [17].…”

A novel assay for 5′-nucleotidase using 1,N6-etheno-AMP as substrate, and comments on the properties of the reaction product, ethenoadenosine

“…These were obtained and treated as described by Woodward & Saggerson (1986) and Jamal & Saggerson (1987). In addition, 1,NM-ethenoadenosine, 1,NM-etheno-5'-AMP and concanavalin A were from Sigma Chemical Co., Poole, Dorset, U.K.…”

“…Brown adipocytes were isolated from the interscapular depot of the same animals (Woodward & Saggerson, 1986) by the procedure originally described by Fain et al (1967) and elaborated by Nedergaard & Lindberg (1982). Preparation of white-adipocyte extracts Preparations of white adipocytes from two rats were washed twice in 10 ml of buffer (45 mM-Tris/HCl/ 45 mM-,f-glycerophosphate, pH 7.4).…”

“…Measurements of white-adipocyte lipolysis and brown-adipocyte 02 uptake were made as described by Saggerson (1986) and Woodward & Saggerson (1986) respectively. T.I.c.…”

“…Effects of ethenoadenosine at adipocyte adenosine receptors Ifetheno-AMP were to be used to assay 5'-nucleotidase in whole-tissue preparations, it is of use to know whether the resulting ethenoadenosine has effects at tissue adenosine receptors which could cause extensive changes in tissue metabolism. Adenosine is antilipolytic in white and brown adipose tissues, and decreases 02 uptake in brown adipocytes (Saggerson, 1986;Woodward & Saggerson, 1986), and these effects appear to be mediated through Al-type receptors. Fig.…”