Hormonal activation of phosphorylase in cockroach fat body trophocytes: A correlation with trans-membrane calcium flux.
This study is an investigation of the temporal relationship between transmembrane Ca(2+) fluxes, and glycogen phosphorylase activation in dispersed trophocytes from the fat body of the cockroach, Periplaneta americana. Phosphorylase is maximally activated within 5 min after treating the trophocytes with either of the hypertrehalosemic hormones, Pea-HTH-I and Pea-HTH-II. Activation caused by Pea-HTH-II is sustained for a longer period than that produced by Pea-HTH-I. Chelation of extracellular Ca(2+) with EGTA blocks the activation of phosphorylase by HTH. Similarly, chelation of intracellular Ca(2+) with Quin 2 greatly diminishes the phosphorylase activating effect of both HTHs. The data support the view that an increase in the intracellular Ca(2+ )concentration is required for the activation of phosphorylase and that extracellular Ca(2+) is an essential, although not necessarily sole, source of Ca(2+) for this purpose. Using (45)Ca(2+) to trace the movement of Ca(2+) following a challenge with either Pea-HTH-I or -II, it was shown that (45)Ca(2+)influx nearly doubled during the first 30 s. At this time, the trophocytes begin to expel Ca(2+) at a rate higher than that of untreated cells and this state persists for approximately 4 min. The Ca(2+) fluxes are consistent with its postulated role in the activation of phosphorylase. Arch.
Steele
J E
JE
Department of Zoology, University of Western Ontario, London, Ontario, Canada. jsteele@julian.uwo.ca
Ireland
R
R
D000634:Aminoquinolines / Q000737:chemistry; D000818:Animals; D000001:Calcimycin / Q000737:chemistry; D002118:Calcium / Q000378:metabolism*; D002132:Calcium Radioisotopes; D002614:Chelating Agents / Q000737:chemistry; D004533:Egtazic Acid / Q000737:chemistry; D004789:Enzyme Activation; D005216:Fat Body / Q000201:enzymology*; D005456:Fluorescent Dyes / Q000737:chemistry; D007301:Insect Hormones / Q000502:physiology*; D007476:Ionophores / Q000737:chemistry; D008297:Male; D010526:Periplaneta / Q000201:enzymology*; D006005:Phosphorylases / Q000032:analysis / Q000378:metabolism*; D012588:Scintillation Counting; D013997:Time Factors
D000634:Aminoquinolines; D002132:Calcium Radioisotopes; D002614:Chelating Agents; D005456:Fluorescent Dyes; D007301:Insect Hormones; D007476:Ionophores; D000001:Calcimycin; D004533:Egtazic Acid; D006005:Phosphorylases; C035739:Quin2; D002118:Calcium