The effect of temperature on post-prandial protein synthesis in juvenile barramundi, Lates calcarifer Robin S. Katersky a, ⁎, Chris G. Carter b a University of Tasmania, National Centre for Marine Conservation and Resource Sustainability, Locked Bag 1370, Launceston, Tasmania 7250, Australia b University of Tasmania, Tasmanian Aquaculture and Fisheries Institute, Locked Bag 49, Hobart, Tasmania 7001, Australia abstract article info Article history: Received 8 February 2010 Received in revised form 13 April 2010 Accepted 14 April 2010 Available online 18 April 2010 Keywords: Lates calcarifer Post-prandial metabolism RNA Specific dynamic action The experiment aimed to measure post-prandial protein synthesis at three different temperatures. Juvenile barramundi (10.81 ± 3.46 g) were held at 21, 27 and 33 °C and fed to satiation daily. Samples were taken over a 24 h period at 0 (24 h after the previous meal) and then at 4, 8, 12 and 24 h after feeding to measure protein synthesis in the white muscle, liver and remaining carcass. Protein synthesis at 27 and 33 °C peaked 4 h after feeding in all tissues and returned to pre-feeding rates by 12 h. At 21 °C protein synthesis remained constant over 24 h in all tissues. While the concentration of RNA remained stable over the 24 h cycle and across temperatures, the ribosomal activity increased after feeding. This meant k RNA , not the absolute amount of RNA, was the driving force underlying the post-prandial increase in protein synthesis. However, relative differences in protein synthesis between tissues were attributed to differences in RNA concentration. There was a significant positive relationship between white muscle and whole body protein synthesis. This was the first study to show an interaction between temperature and the time after feeding on protein synthesis for an ectotherm, and that a post-prandial peak in protein synthesis only occurred under optimum temperature conditions. © 2010 Elsevier Inc. All rights reserved. 1. Introduction Protein synthesis occurs in all living organisms and is the underlying process driving growth. Many factors, both biotic and abiotic, affect this process. However, temperature is the key abiotic factor that controls the growth rate of ectotherms (Brett and Groves, 1979; Elliott, 1994; Jobling, 1997; McCarthy and Houlihan, 1997). It is generally accepted that protein synthesis will increase with increasing temperature when an unlimited supply of food is available and the temperature increase is within the thermal tolerance range (Houli- han, 1991; McCarthy and Houlihan, 1997 Carter et al., 2001). Temperature, feed intake, growth and protein synthesis are interconnected. Temperature drives metabolic demand and therefore feed intake which in turn drives protein synthesis and consequently growth. Protein synthesis occurs in all tissues at varying rates with the fish liver having the highest rate of synthesis and the white muscle the lowest (Fauconneau and Arnal, 1985; Houlihan et al., 1988; Carter and Houlihan, 2001). The contribution that the liver and white muscle make to whole body protein synthesis is significant, albeit for different reasons, and the combination of tissue protein mass and rate of synthesis means that the white muscle and liver account for the majority of whole body protein synthesis. Whole body protein synthesis has been shown to account for as much as 42% of the energy expenditure of feeding fish (Houlihan et al., 1988). After feeding a post-prandial increase in protein synthesis occurs (Lyndon et al., 1992; McMillan and Houlihan, 1989) as part of specific dynamic action (SDA) (Carter et al., 2001; McCue, 2006; Secor, 2009). SDA is generally determined by measuring the time course of oxygen consumption after a meal and post-prandial increases in oxygen consumption correspond with increases in protein synthesis (Carter and Brafield, 1992; Lyndon et al., 1992). Oxygen consumption increases with increased temperature and is reflected in a linear increase in tissue protein synthesis (McCarthy and Houlihan, 1997). The post-prandial pattern in whole body protein synthesis is a composite of protein synthesis in different tissues which respond maximally to feeding at different times and this is reflected in the SDA profile (Houlihan, 1991; Carter et al., 2001). Liver metabolic rate is high and the rapid response to feeding in protein synthesis is thought to influence when the peak SDA occurs (Secor, 2009). Whilst white muscle protein synthesis may have the lowest rate of all tissues, it has the largest tissue mass and is a major contributor to whole body protein synthesis rates (Houlihan et al., 1988) and therefore to SDA (Lyndon et al., 1992). Protein synthesis in the liver and white muscle increase with temperature at similar rates indicating that there is a single temperature response regardless of the relative rates of protein synthesis (McCarthy and Houlihan, 1997). By measuring the post- Comparative Biochemistry and Physiology, Part A 156 (2010) 529–536 ⁎ Corresponding author. Tel.: + 61 3 6324 3824; fax: + 61 3 6324 3804. E-mail address: robin.katersky@utas.edu.au (R.S. Katersky). 1095-6433/$ – see front matter © 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.cbpa.2010.04.009 Contents lists available at ScienceDirect Comparative Biochemistry and Physiology, Part A journal homepage: www.elsevier.com/locate/cbpa