Dynamics of metabolic responses to prolonged elevation of circulating adrenaline in resting and exercising rats

The purpose of this study was to follow the time course of metabolic responses to hyperadrenalinemia sustained up to 3 days. Hyperadrenalinemia was produced in rats by s.c. implantation of tablets releasing adrenaline (A) at a constant rate (1.6 micrograms x min-1). After 6, 12, 24 and 72 h of hyperadrenalinemia and 3 days after the tablet removal rats were sacrificed and liver, 3 types of muscles and blood samples were taken. Each time 14 rats were used: 7 of them were sedentary and 7 performed treadmill endurance exercise before decapitation. Sham operated animals served as controls. In preliminary experiments working ability was examined in 10 hyperadrenalinemic and 10 control rats. Duration of exercise until exhaustion was reduced in hyperadrenalinemic rats on the average by 40%. In sedentary rats, hyperglycemia, marked depletion of liver glycogen (by approx. 80%) and muscle glycogen (by 60-80%) as well as an elevation (2-4 times) of muscle lactate (LA) were found only during the first day after A-tablet implantation. At the end of the experiment these values approached the control ones. Muscle contents of ATP and creatine phosphate (CrP) were decreased by approx. 20% and 30-60%, respectively. Plasma FFA were markedly enhanced, varying in the time-course of the experiment from 0.8 to 1.4 mmol x l-1. Post-exercise values for blood glucose, liver and muscle glycogen were always lower in hyperadrenalinemic rats than in controls sacrificed after time-matched exercise (30 min). Circulating FFA decreased during exercise at all time points following A-tablet implantation, but they were still above the post-exercise levels in sham-operated rats.(ABSTRACT TRUNCATED AT 250 WORDS)