Seasonality of the red blood cell stress response in rainbow trout (Oncorhynchus mykiss)

Koldkjær, P.; Pottinger, T.G.; Perry, S.F.; Cossins, A.R.. 2004 Seasonality of the red blood cell stress response in rainbow trout (Oncorhynchus mykiss). Journal of Experimental Biology, 207. 357-367. 10.1242/jeb.00747

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Abstract/Summary

The β-adrenergic stress response in red blood cells (RBCs) of rainbow trout shows seasonal changes in expression. We have explored the mechanisms underpinning this response by following over a period of 27 months changes in β-adrenergic receptor (β-AR) binding characteristics, β-adrenergically stimulated RBC Na+/H+ exchanger (βNHE) activity, together with β-AR and βNHE mRNA levels and plasma steroid hormone and lactate levels. These parameters were measured at approximately monthly intervals in a single population of fish held under semi-natural conditions. Membrane-bound, high-affinity β-ARs were present in RBCs at all sampling times, varying from 668 ± 112 to 2654 ± 882 receptors cell-1 (mean ± SEM; n=8). βNHE activity, however, was reduced by 57 and 34% in December 1999 and February 2001, respectively, compared to an otherwise sustained influx that averaged 110.4 ± 2.3 mmol l-1 RBCs h-1 (n = 119). Only one reduction coincided with a spawning period but both were preceded by transient increases in circulating testosterone. βNHE activity measured under standard conditions was not correlated with the number or affinity of β-ARs nor with water temperature, but both β-AR numbers and βNHE activity were positively related to their respective mRNA levels (P = 0.005 and 0.038, respectively). Pharmaceutical intervention in the transduction cascade linking the β-AR and βNHE failed to indicate any failure of the transduction elements in RBCs displaying low βNHE activity. Similarly, we failed to demonstrate any link between seasonal cortisol fluctuations and seasonally reduced βNHE activity. However, the βNHE activity of age-separated RBC fractions showed that younger RBCs had a significantly higher βNHE response than older RBCs, consistent with the seasonal reductions in βNHE being linked to turnover of red cells and erythropoiesis. Testosterone is known to induce erythropoiesis and we conclude that seasonal reductions in βNHE are not caused by changes in β-AR numbers, but may be linked to testosterone-induced erythropoiesis.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1242/jeb.00747
Programmes:	CEH Programmes pre-2009 publications > Water
UKCEH and CEH Sections/Science Areas:	_ Environmental Chemistry & Pollution
ISSN:	0022-0949
Additional Information. Not used in RCUK Gateway to Research.:	Click on the OFFICIAL URL link to access freely available full text of paper.
Additional Keywords:	adrenergic receptor, Na+/H+ exchanger, estradiol, testosterone, cortisol, seasonal changes
NORA Subject Terms:	Ecology and Environment Zoology Biology and Microbiology
Date made live:	15 Jun 2015 11:00 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/510678

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