The prolonged effects of acute exercise on the plasma concentrations of FFA, glycerol, glucose and catecholamines were examined. Twelve young men performed exhaustive prolonged exercise on a cycle ergometer (80 minutes at 70-75% of VO2 max), and in separate experiments they exercised for shorter durations (20, 40 and 80 minutes) and at lesser intensities (29, 50 and 75% of VO2 max). Carbohydrate-rich meals were given 2, 7 and 12 hours after exercise. Blood samples were taken while the subjects rested in bed during a 12-14-hour recovery period. Control experiments without exercise were also performed. In some subjects the plasma concentration of FFA after exhaustive exercise was increased to levels considered to be potentially hazardous, and the mean plasma level of FFA was increased for 6 hours and that of glycerol was increased for 2.5 hours after exercise. The plasma concentration of glucose was generally reduced for 12 hours after exhaustive exercise. Plasma catecholamines were increased for 2 hours after exhaustive exercise. We observed a preprandial increase in FFA and glycerol concentrations during recovery from exercise which was related to the duration and intensity of exercise. These findings indicate that the rates of FA utilization and TG-FA substrate cycling were increased in the recovery period after exercise, and that the magnitude of both depends on the duration and intensity of exercise.

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1 Variable results have been reported on the effect of P-adrenoceptor blockers on maximal oxygen uptake (Vo, max) and exercise endurance. This may in part be due to different subject populations, but it could also be due to an adaption of metabolic and haemodynamic responses to exercise during chronic treatment with P-adrenoceptor blockers. The present study was therefore carried out to examine the effect of acute and chronic administration of the non-selective P-adrenoceptor blocker propranolol on both peak Vo2 and exercise performance in the same subjects. Since the effect of P-adrenoceptor blockade has not been properly investigated in women, eight healthy women were compared with seven men. Progressive bicycle exercise to exhaustion was performed after propranolol 0.15 mg kg-' i.v. (acute) or 80 mg three times daily for 2 weeks (chronic) or placebo given according to a double-blind crossover design. 2 Mean (s.e. mean) peak Voz, was significantly reduced from 42.3 (1.6)ml min-' kg-' during placebo to 40.3 (1.2, P

1. The properties of protein kinase in extracts of rat diaphragm has been studied. Investigations on protein kinase has also been made after preincubation of the diaphragms with epinephrine or insulin. Protein kinase activity was measured by the rate of incorporation of 32P from [y-32P]ATP into histone in the absence and the presence of cyclic AMP. I n addition the binding of cyclic [3H]AMP by the extracts was investigated. Furthermore, the cyclic-AMP-dependent and -independent enzymes were separated by gel filtration on Sephadex G-150.2 . Protein kinase activity in crude extracts was increased 2-to %fold by cyclic AMP. The cyclic-AMP-dependent activity was relatively stable during purification with ammonium sulphate and recovered to an extent of 70°/,. The cyclic-AMP-dependent activity in crude extracts was recovered as a separate peak by gel filtration on SephadexG-150. Purified cyclic-AMPdependent protein kinase was quantitatively recovered when added to a crude muscle extract. It is indicated that the cyclic-AMP-dependent protein kinase in muscle extracts quantitatively reflects the amount of the inactive holoenzyme in the tissue.3. Protein kinase activity independent of cyclic AMP was inactivated by crude muscle extracts.This was demonstrated by preincubation of muscle extracts with cyclic AMP. Dissociation of the holoenzyme by cyclic AMP as demonstrated by a decrease of cyclic-AMP-dependent activity and a decreased binding of cyclic [3H]AMP was not accompanied by a change in the cyclic-AMPindependent activity. Purified cyclic-AMP-independent protein kinase added to crude muscle extracts was also inactivated. A small peak of cyclic-AMP-independent activity was obtained when crude extracts were subjected to gel filtration on Sephadex G-150. This peak was increased 2-to 3-fold when elution was done in the presence of 0.5 M NaC1. It is indicated that the active catalytic subunit of protein kinase in the tissue mainly is converted to an inactive complex in muscle extracts. 4.After preincubation of rat diaphragms with epinephrine the cyclic-AMP-dependent activity as well as the binding of cyclic [3H]AMP were decreased. This was demonstrated both in crude muscle extracts and in purified enzyme preparations of protein kinase from the extracts. 5 . After preincubation of rat diaphragms with insulin the opposite effects could be demonstrated. Both in crude extracts and purified enzyme preparations the binding of cyclic [3H]AMP and the cyclic-AMP-dependent protein kinase activity were increased.6. By gel filtration of rat diaphragm extracts on Sephadex G-150 it was demonstrated that preincubation of the diaphragms with epinephrine resulted in decreased cyclic-AMP-dependent protein kinase, whilst the cyclic-AMP-independent enzyme was increased. The opposite effects were seen by preincubation of the diaphragms with insulin, i.e. increased cyclic-AMP-dependent and decreased cyclic-AMP-independent enzymes. 7 . It is indicated that important metabolic effects by epinephrine and insulin are mediated by modulation of the ac...