Phosphorylase activity in needle biopsy samples--factors influencing transformation.
Phosphorylase was determined in biopsy samples frozen immediately or after a delay of 10 s to 6 min. Muscle biopsies were performed at rest without and with propranolol, or adrenalin infusion and after electrical stimulation. The phosphorylase a fraction was 36% (28-44) in resting samples frozen immediately and 12% (12-13) after 10 s delay and remained at the same level when the freezing was further delayed (up to 6 min). It is suggested that an increase in [Ca2+] in the cytoplasm due to the insertion of the needle in muscle or cutting of tissue membranes may cause transformation of phosphorylase from b to a form, a transformation which is restored when Ca2+ is pumped back during the delay. Also the increased phosphorylase a fraction observed in biopsy samples obtained during adrenalin infusion reverted partially back when freezing was delayed for 10 s and 30 s, respectively. In muscle samples taken during contraction the mole fraction of phosphorylase a decreased from 53 to 12% when freezing was delayed for 10 s. The lowest value of the phosphorylase a mole fraction was observed in resting muscle after beta-blockade when the tissue samples were frozen 10 s after sampling and corresponded to 10% of the total phosphorylase. It is concluded that both muscle sampling and circulating adrenalin will increase phosphorylase a fraction in resting muscle and probably also augment the effect of adrenalin infusion.
Ren
J M
JM
Department of Clinical Chemistry II, Karolinska Institutet, Huddinge University Hospital, Sweden.
Hultman
E
E
D000328:Adult; D004558:Electric Stimulation; D004837:Epinephrine / Q000494:pharmacology; D005615:Freezing; D006801:Humans; D008297:Male; D009119:Muscle Contraction; D009132:Muscles / Q000201:enzymology*; D010762:Phosphorylase a / Q000378:metabolism*; D006005:Phosphorylases / Q000378:metabolism*; D011433:Propranolol / Q000494:pharmacology; D013997:Time Factors
D011433:Propranolol; D010762:Phosphorylase a; D006005:Phosphorylases; D004837:Epinephrine