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© Georg Thieme Verlag KG Stuttgart · New York
Gluconeogenesis and Hepatic Glycogen Formation in Relation to the Rat Estrous Cycle
08 January 2009 (online)
Alterations in in vivo gluconeogenesis and hepatic glycogen synthesis were examined in relation to the rat estrous cycle. In vivo gluconeogenesis was evaluated by following incorporation of intravenously administered UL-14C-alanine into blood glucose over a 30 minute period. Gluconeogenesis was significantly elevated at diestrus in comparison to the other stages of the estrous cycle. Increased gluconeogenesis in this group corresponded with elevated blood glucose levels and decreased serum insulin levels.
Alterations in hepatic glycogen formation during the estrous cycle followed a different pattern than that seen for gluconeogenesis. Hepatic glycogen content was highest at proestrus, dropping to low levels at estrus and then increasing slightly during metestrus and diestrus. This pattern coincides with variations in plasma glucocorticoid levels noted by others during the estrous cycle. These results demonstrate that the fluctuations in plasma levels of the ovarian steroids during the estrous cycle are sufficient to cause alterations in gluconeogenesis and hepatic glycogen metabolism. It is suggested that these metabolic alterations during the estrous cycle result from the effects of gonadal steroids on pancreatic and adrenocortical secretions.
Gluconeogenesis - Glycogen Synthesis - Estrous Cycle - Estradiol - Progesterone - Insulin