High Blood Cortisol Levels and Low Cortisol Receptor Affinity: Is the Chub, Leuciscus cephalus, a Cortisol-Resistant Teleost?

Abstract

The NERC and CEH trademarks and logos ('the Trademarks') are registered trademarks of NERC in the UK and other countries, and may not be used without the prior written consent of the Trademark owner. ABSTRACTIn contrast to the relatively minor intra-and inter-species differences in blood cortisol levels reported for salmonid species, there is a more pronounced distinction between cortisol levels among the Salmonidae and Cyprinidae, with both basal and stressinduced cortisol levels markedly higher in the latter. This study shows that in the chub, Leuciscus cephalus, a widely distributed European cyprinid, mean blood cortisol levels during stress (1500 ng ml -1 ) exceeded those reported for most other species of fish and even in unstressed chub, cortisol levels (50 -100 ng ml -1 ) were within the range known to cause immunosuppression, growth retardation and reproductive dysfunction in salmonid fish. The chub appears to be atypical only with respect to plasma cortisol levels; the levels of plasma glucose and plasma lactate in unstressed and stressed chub are similar to those reported for other species. Plasma levels of 11-ketotestosterone in males and 17-estradiol in females are lower than reported for salmonids but similar to other cyprinid species and display clear stressinduced reduction. Comparative analysis of the binding characteristics of the trout and chub gill cortisol receptor revealed that the total number of binding sites in gill tissue for each species was similar (Bmax; ~50 -100 fmol mg -1 protein). However, the affinity of the binding site for cortisol displayed an 8-fold difference between the species (rainbow trout: Kd ~ 6 nM; chub: Kd ~ 50 nM). Therefore, the potentially adverse effects of high circulating levels of cortisol found both at rest and under conditions of stress in chub may be offset by the lower affinity of the cortisol receptor, rather than the abundance of target-tissue receptor sites. This strategy is similar to that reported for some glucocorticoid-resistant rodent species and New World primates.3

Effect of nutritional status and sampling intensity on recovery after dorsal aorta cannulation in free-swimming Atlantic salmon (Salmo salar L.)

“…In fact, there are certain numbers of experiments reporting resting levels even higher than 50 ng ml -1 (Barton and Iwama 1991;Gamperl et al 1994b). The higher resting levels could arise due to differences in assay specificity, husbandry conditions, capture procedure, and other external and internal factors (Bonga 1997;Pottinger et al 2000). Under certain circumstances, low cortisol levels may even indicate a stress condition (Vijayan and Leatherland 1990), illustrating the difficulty of using a cortisol as a sole variable to distinguish between a stressed and a non-stressed state.…”

The three‐spined stickleback as an environmental sentinel: effects of stressors on whole‐body physiological indices

“…Pottinger et al, 2000), a response that is believed to reflect primarily the glycogenolytic and gluconeogenic actions of catecholamines -the role of cortisol in stress-induced hyperglycaemia has not been confirmed (Pickering & Pottinger, 1995). It is assumed that sticklebacks display a similar hyperglycaemic response to stress (although no data exist to substantiate this) reflecting a requirement for mobilisation of energy during stress.…”

Influence of cortisol on osmoregulation and energy metabolism in gilthead seabream Sparus aurata

“…The actions of cortisol on the energy metabolism of tissues other than liver, such as the gills (Pottinger et al, 2000), brain (Knoebl et al,'96), or kidney (Kloas et al,'98), in which receptors for cortisol have been described, have been less studied to date (Mommsen,'84;Mommsen et al,'99).…”