Kinetics ofin VivoGlycogen Synthesis in the Estrogen-Stimulated Rat Uterus

Abstract

Characterization of in vivo glycogen synthesis in the rat uterus after estrogen administration revealed: a) an initial lag phase of less than 2 hr; b) a period, from 2 to 10 hr, when glycogen concentrations increased at a constant rate; c) an equilibrium period from 10 to 24 hr, followed by: d) a decline in glycogen concentration approximately 24 hr after estrogen administration. The glycogen synthesis induced by 1 μg of estradiol, which was 3 to 4 times control levels at 10–12 hr, appeared to be maximal. Larger doses (10 μg) of estradiol or repeated estrogen injections did not result in a reaction rate different from that observed with 1 μg, suggesting that maximal stimulation of the glycogenic systems had probably been attained. Glycogen synthesis adhered to first order reaction rate kinetics. The rate constant (K) was 1.94 ×1O^-3 min^-1, which resulted in an increase in glycogen synthesis of about 12% each hour. (Endocrinology76: 63, 1965)