Skeletal muscle carbohydrate metabolism during short-term and prolonged in vivo electrical stimulations.

Electrical stimulations were applied to the gastrocnemius muscle of intact frog. Rana hexadactyla (Lesson) for short-term (SMS) and prolonged (PMS) periods. Short-term muscular stimulations resulted in decreased glycogenolysis and glycolysis with depleted glycogen and lactic acid contents in the muscles and increased lactic acid content in the blood. The activity levels of SDH and MDH were decreased in SMS muscles. Prolonged muscular stimulations, on the other hand, increased glycogenolysis and glycogenolysis was suggested to be due to stepped-up glycogenesis. Tissue oxidative metabolism was also correlated with regulation of activities of enzymes concerned with anaerobic pathways.

Induction of riboflavin-carrier protein in the immature male rat by estrogen: kinetic and hormonal specificity.

The kinetics of estrogen-induced accumulation of riboflavin-carrier protein in the plasma was investigated in immature male rats using a specific and sensitive homologous radioimmunoassay procedure developed for this purpose. Following a single injection of the steroid hormone, plasma riboflavin-carrier protein levels increased markedly after an initial lag period of approximately 24 h, reaching peak levels around 96 h and declining thereafter. A 1.5 fold amplification of the inductive response was evident on secondary stimulation with the hormone. The magnitude of the response was dependent on hormonal dose, whereas the initial lag phase and the time of peak riboflavin-carrier protein induction were unaltered within the range of the steroid doses (0.1-10 mg/ kg body wt.) tested. Simultaneous administration of progesterone did not affect either the kinetics or the maximum level of the protein induced. The hormonal specificity of this induction was further adduced by the effect of administration of antiestrogens viz., En and Zu chlomiphene citrates, which effectively curtailed hormonal induction of the protein. That the induction involved de novo-protein synthesis was evident from the complete inhibition obtained upon administration of cycloheximide. Passive immunoneutralization of endogenous riboflavin-carrier protein with antiserum to the homologous protein terminated pregnancy in rats confirming the earlier results with antiserum to chicken riboflavin-carrier protein.