ALBERT

Description: Data derived from a study aimed to detect differences in thermal tolerance by investigating the underlying metabolic responses in the green abalone (Haliotis fulgens) under conditions of hypoxia and hypercapnia. Juvenile abalones were exposed to a temperature ramp (+3 °C day−1) under hypoxia (50% air saturation) and hypercapnia (~1000 μatm pCO2), both individually and in combination. Impacts on energy metabolism were assessed by analyzing whole animal respiration rates and metabolic profiles of gills and hepatopancreas via 1H NMR spectroscopy. The experiments are depicted as warming (warming ramp under normoxic normocapnia), hypoxia (warming ramp under hypoxic normocapnia), hypercapnia (warming ramp under normoxic hypercapnia), and combined (warming ramp under hypoxic hypercapnia). Each experiment was accompanied by a Control group, which was exposed to the same water PO2 and PCO2 but at a stable temperature (18 °C).

Description: Temperature dependent growth is an important indicator to understand the thermal tolerance of organisms and to project their vulnerability to future climate change. Direct measurements of temperature dependent weight gains, however, are experimentally challenging and time consuming in long-lived species. Here, we reassess methodology to quantify the in vivo protein synthesis rate from amino acids, as a key component of growth. We developed an analytical method that is both robust against analytical errors and does not require hazardous radioactive materials. We utilized the incorporation of isotopically 13C15N-labeled-phenylalanine into fish muscle followed by quantification by liquid chromatography mass spectrometry to calculate accurate net protein synthesis rates in muscle tissue of Antarctic fish, Pachycara brachycephalum, in vivo. Specifically, we injected 150 mM of 13C9H915N1 phenylalanine intraperitoneally and sampled muscle tissue in 1,5h steps between 0 and 6 hours after injection. We quantified labeled and unlabeled phenylalanine both in muscle protein and in the cytosol. This allowed us to critically re-evaluate three different protein synthesis rate (Ks) calculation methodologies that have been developed over the last decades. The calculated values differ by more than 70-fold (0.048 ± 0.021% day-1 up to 3.56 ± 2.16 day-1) between methods. We argue that the Ks calculation including a proportionate ratio of protein synthesis from (unlabeled) free amino acids yields the most realistic Ks values for cold water fish. Eventually, the standardization of the net protein synthesis rate calculation will lead to dependable quantitative representations of organismal stress in response to climate change.