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Estradiol Modulates Adrenal Nerve Activity and Plasma Epinephrine Clearance
Author(s) -
Adams Julye M,
Stocker Sean D,
Ott Cobern E,
Jackson Brian A
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a300-c
Subject(s) - medicine , endocrinology , epinephrine , catecholamine , hypoglycemia , chemistry , insulin
Previous work from this laboratory has established that hypoglycemia‐induced increases in plasma epinephrine (EPI) concentration are significantly greater in 14‐day ovariectomized (OVEX) rats compared to estrogen‐replaced OVEX rats (OVEX+E2) suggesting that physiological levels of circulating 17β‐estradiol (E2) can modulate this stress response. The aim of the present study was to determine whether this effect of E2 is due to a reduction in stress‐induced adrenal sympathetic nerve activity (SNA), which is the primary trigger for EPI secretion, or due to an increase in plasma EPI clearance. Insulin (0.25 U/kg, i.v.) decreased plasma glucose concentration to the same extent in anesthetized OVEX and OVEX+E2 rats (‐50± 6 and −47± 4 mg/dL; P<0.001). However, the increase in adrenal SNA was significantly greater in OVEX+E2 rats compared to OVEX at 30 min post insulin (79± 11% vs 32± 8%; P<0.01). To determine whether plasma EPI clearance can be modulated by E2, plasma EPI concentrations were compared in both OVEX and OVEX+E2 groups before and during three 30 min sequential EPI infusions of 600, 1500, and 3000 pmol/kg/min. Pre‐infusion plasma EPI did not differ between the groups (108 ± 19 vs. 92 ± 9 pg/mL). The increase in plasma EPI concentration at each dose was significantly attenuated in OVEX+E2 rats (600:Δ−39%, 1500:Δ,−34%, 3000:Δ−42%; P<0.05), suggesting that the rate of EPI clearance is greater in OVEX+E2 compared to OVEX rats. The present study demonstrates that physiological levels of E2 can modulate both adrenal SNA and the clearance of plasma EPI, however, only the latter is consistent with the observed suppressive effect of E2 on hypoglycemia‐induced increases in plasma EPI levels.