Hypercapnic and hypocapnic hypoxia in the lugworm arenicola marina: A ³¹P NMR study

Abstract

Using the noninvasive method of 31P nuclear magnetic resonance (NMR) spectroscopy, the influence of hypoxia on intracellular pH (pH,) and on the energy metabolism was studied in the lugworm Arenicola marina.1. During hypercapnic hypoxia (induced by the animal itself), pH, dropped from 7.3 +-0.1 (n = 6) to 6.5 k 0.1 (n = 4) within 24 hours, whereas during hypocapnic hypoxia pHi decreased by only 0.3 units (n = 4). The change in pH, (pH of the ambient water) was similar: strong acidification from about 8.1 to 6.1 during hypercapnic and moderate acidification to 7.8 during hypocapnic hypoxia.2. Mobilization of phosphagen (phosphotaurocyamine) occurred faster during hypercapnic than hypocapnic hypoxia. Anaerobic end products (propionate and acetate), however, accumulated to a greater extent during hypocapnic than hypercapnic hypoxia.3. Conclusion: The severe acidosis found during hypercapnic hypoxia depends on the amount of C 0 2 accumulation rather than on the amount of glycolytic end products. On the other hand, the lower accumulation of glycolytic end products and the faster mobilization of phosphagen with severe acidosis seem to reflect a regulatory effect of pHi on anaerobic metabolism.Several invertebrates belonging to different phyla have been shown to survive prolonged periods of experimental and environmental hypoxia; i.e., they are facultative anaerobes (for review, see de Zwaan and van den Thillart, '85; Zebe and Schottler, '86). The pathways of energy production during prolonged anaerobiosis have been studied thoroughly, particularly in the sea mussel Mytilus edulis (for review, see de Zwaan and van den Thillart, '85) and in the lugworm ArenicoZa marina (Grieshaber and Kreutzer, '86; Schottler, '86). From these studies it is evident that a sufficient energy supply for surviving prolonged periods of hypoxia depends on two mechanisms: 1) the depression of the metabolic rate and 2) the switch of the glycolytic pathway toward the formation of volatile fatty acids resulting in a yield of adenosine triphosphate ( ATP) substantially higher than from formation of lactic acid.Several hypotheses have been published to explain how depression of the metabolic rate may be attained and which regulatory mechanisms could bring about the switch of glycolysis at the phosphoerolpyruvate (PEP) branchpoint during the first hours of hypoxia. In this respect, the role of 0 1989 ALAN R. LISS, INC.

Combined effects of temperature and emersion-immersion cycles on metabolism and bioenergetics of the Pacific oyster Crassostrea (Magallana) gigas

“…insufficient to fully compensate for the breakdown in the digestive gland of the oysters exposed to hypoxia-heat combination. Apart from that, our findings agree with the earlier studies that report enhanced carbohydrate metabolism during hypoxia in human endothelial cells (Oehler et al, 2000), polychaetes (Kamp and Juretschke, 1989) and bivalves (Isani et al, 1989;Greenway and Storey, 1999). Arginine biosynthesis was modulated in all exposure groups demonstrated by shifts of the key amino acids Asp, Gln, Glu and citrulline.…”

The lugwormArenicola marina: A model of physiological adaptation to life in intertidal sediments

“…Although this clearly affected some processes (Kamp & Juretschke, 1989a), it appears insufficient to account for the observed decline of the metabolic rate. Nine to twelve hours after the onset of hypoxia, the switching from aerobic to anaerobic metabolism is complete.…”

“…Its breakdown results in an increase of inorganic phosphate which can be observed in intact animals by means of 13p-NMR spectroscopy (Kamp & Juretschke, 1989a). Concomitantly, degradation of glycogen is activated as shown by 13C-NMR technique (Juretschke & Kamp, 1990a).…”