ISSN:
1432-136X
Keywords:
Hypoxia
;
Regulation of glycogenolysis
;
Inorganic phosphate
;
Free adenosine monophosphate
;
Lugworm, Arenicola marina
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Abstract The cytoplasmic concentrations of free inorganic phosphate and free AMP in the body wall of the lugworm Arenicola marina were estimated in order to verify their proposed regulatory role in glycogenolysis during anaerobiosis (Kamp 1993). Using in vivo 31P nuclear magnetic resonance spectroscopy the concentration of free inorganic phosphate was determined to be 4.7±0.7 mmol·1-1 (±standard deviation, n=3) varying with season (Juretschke and Kamp 1995). These values were two to three times lower than those measured in perchloric acid extracts. In contrast, values for the phosphagen phosphotaurocyamine assessed biochemically in the extracts and by in vivo nuclear magnetic resonance were very similar. During the transition from normoxia to hypoxia the concentration of free inorganic phosphate increased to the same extent and at the same rate as the concentration of phosphotaurocyamine decreased. A discrepancy was also found for the biochemically determined AMP and ADP concentrations in the extract and those derived from the equilibrium constants of the taurocyamine kinase (ADPfree) and adenylate kinase (AMPfree) reactions. Calculated concentrations of ADPfree and AMPfree in normoxic specimens were about two or even four orders of magnitude lower than the values determined in extracts. During hypoxia the concentrations of AMP and ADP increase moderately when measured biochemically in extracts, while the values for ADPfree and AMPfree rise three- and nine-fold during the first 3 h of hypoxia. Thereafter, the levels stay constant due to a progressive acidosis. If during hypoxia pHi is stabilized by addition of buffering substances to the incubation medium, both ADPfree and AMPfree rise continuously. The significant changes found for the concentrations of free inorganic phosphate and AMPfree support their assumed regulatory role in glycogenolysis during anaerobiosis, though these AMPfree values seem too low to actually activate glycogen phosphorylase. The strong effect of pHi on the levels of ADPfree and AMPfree suggest a mechanism by which acidosis prevents a continuing increase of glycogenolysis (ATP-producing pathway) during prolonged anaerobiosis (protective effect of acidosis).
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00301478
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