Metabolic Regulation of Fast- and Slow-twitch Skeletal Muscles by Estradiol and Progesterone in Females and their Impact during Ischemia
Year: 2014
Type: dissertation
Abstract: The roles of estradiol and progesterone were investigated to determine the effect of these hormones on metabolism in skeletal muscle composed of different fiber types (slow-twitch, fast-twitch and their various sub-types) which have different metabolic properties. The metabolic implications of these sex hormones were also tested under ischemic conditions. Female Sprague-Dawley rats were ovariectomized and given one of the following for 120 days: estradiol (ET), intermittent-estradiol (IE), progesterone (P), both IE and P (IE+P), estrogen receptor (ER) antagonist ICI 182,780 (ICI), selective ER modulator Raloxifene (RLX). Key statistically significant findings included that estradiol decreased glycogen phosphorylase and phosphofructokinase activity in fast-twitch muscles with greater total fast-twitch fiber content. Progesterone decreased in vivo glycogen by 25% in slow-twitch muscles. This response was only found in fast-twitch muscles when IE+P was given. During ischemia, IE+P reduced glycogen consumption irrespective of muscle type, which was attributed to lower in vivo glycogen levels. In vivo creatine phosphate (CP) levels in females given IE+P were reduced by 25%, irrespective of muscle type. Ischemic CP consumption was decreased only in fast-twitch muscles of IE+P females who had lower in vivo CP levels. ER studies established that ICI significantly lowered in vivo CP levels by 70-80% in both fast- and slow-twitch muscles, resulting in reduced ischemic CP consumption. RLX did not appear to modulate metabolism in these studies. These results demonstrated that the principle female sex hormones are important regulators of glycogen and CP metabolism and that the ER blockade decreases CP content in skeletal muscle. Moreover, ovarian steroid hormone regulation of glycogen metabolism is muscle fiber specific, whereas that of CP metabolism is not muscle fiber specific.
Source: TSpace (University of Toronto)
Author: Nesime Askin
Language: English
Subfield: Endocrinology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2472794135