Previously, we also found that transdermal 17bestradiol
administration had no effect on skeletal muscle
glycogen utilization in males (43). The marked
hepatic glycogen sparing (23, 24) and the lack of an
effect on GLUT-4 content (39) suggest that 17b-estradiol
has a more significant effect on hepatic glucose
production than on skeletal muscle glucose uptake.
These observations are similar to animal data demonstrating
muscle and hepatic glycogen sparing (23, 24)
and increased lipid oxidation (18) in 17b-estradiolsupplemented
male or oophorectomized female rats.
In the present study, the lower epinephrine concentration
in females was cotemporal with a lower glucose
MCR at 90 min compared with males. This observation
is similar to the results of Ruby et al. (37), who demonstrated
that the provision of 17b-estradiol to amenorrheic
females reduced plasma epinephrine concentration
during endurance exercise. It is also similar to
previous findings from our laboratory, in which the
17b-estradiol administered to males resulted in a significantly
lower glucose Ra and MCR and a trend (P 5
0.09) toward a decrease in plasma epinephrine concentration
(4).
Previously, we also found that transdermal 17bestradiol
administration had no effect on skeletal muscle
glycogen utilization in males (43). The marked
hepatic glycogen sparing (23, 24) and the lack of an
effect on GLUT-4 content (39) suggest that 17b-estradiol
has a more significant effect on hepatic glucose
production than on skeletal muscle glucose uptake.
These observations are similar to animal data demonstrating
muscle and hepatic glycogen sparing (23, 24)
and increased lipid oxidation (18) in 17b-estradiolsupplemented
male or oophorectomized female rats.
In the present study, the lower epinephrine concentration
in females was cotemporal with a lower glucose
MCR at 90 min compared with males. This observation
is similar to the results of Ruby et al. (37), who demonstrated
that the provision of 17b-estradiol to amenorrheic
females reduced plasma epinephrine concentration
during endurance exercise. It is also similar to
previous findings from our laboratory, in which the
17b-estradiol administered to males resulted in a significantly
lower glucose Ra and MCR and a trend (P 5
0.09) toward a decrease in plasma epinephrine concentration
(4).
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