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Physiological Ecology and Reproductive Endocrinology




Oestradiol and progesterone change β3-adrenergic receptor affinity and density in brown

adipocytesB

AF Malo and M Puerta

European Journal of Endocrinology 145: 87-91     2001

Objective: To check if the oestradiol- and progesterone-driven reduction in noradrenaline responsiveness of brown adipocytes is due to a reduction in either the density or the affinity of b3-adrenoceptors (b3-AR). b1/b2-AR were also studied. Design: Four groups of animals were considered. (i) control rats at thermoneutrality, (ii) coldacclimated rats, to determine b-AR under continuous sympathetic stimulation, which is known to decrease noradrenaline responsiveness, (iii) oestradiol- and (iv) progesterone-treated cold-acclimated rats to determine hormonal effects on b-AR populations in thermogenically active brown adipocytes.  Methods: Oestradiol and progesterone were chronically elevated by means of s.c. Silastic implants. Densities and affinities of b-AR populations were determined by binding studies using [3H]CGP- 12177 as radioligand. Results: Two populations of low and high binding affinities (Kd 1.6 and 27.3 nmol/l) corresponding to b3- and b1/b2-AR respectively were found at thermoneutrality. b3-AR density was higher than that of b1/b2-AR (Bmax 419 and 143 fmol/mg protein respectively). Cold-acclimated rats showed a reduction of b3-AR binding capacity (Bmax 308 fmol/mg protein). Oestradiol and progesterone reduced the density of b3-AR to 167 and 185 fmol/mg protein respectively, while increasing their affinity for [3H]CGP-12177 (Kd 9.5 and 4.0 nmol/l vs 16 nmol/l in cold-acclimated untreated rats). The density of b1/b2-AR was also reduced after oestradiol treatment (Bmax 51 fmol/mg protein). Conclusions: Both oestradiol and progesterone reduce the density of b3-AR in brown adipose tissue (BAT) while increasing their affinity for [3H]CGP-12177. Oestradiol also reduces the density of b1/b2-AR whereas cold-acclimation reduces the density of b3-AR.



                                                                                                    


Reproductive Endocrinology of The European Badger: Effects on its 

behaviour, Reproduction and Survival


In collaboration with Nadine Sugianto, Dr. Christina Bueshing and  Prof. David MacDonald.


                                                                                                    




Effects of Inbreeding and adaptation to captivity on the response to stress


In collaboration with Dr. Nadja Wielebnowski and Dr. Robert C Lacy.




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