A putative cortisol receptor in the rainbow trout erythrocyte: stress prevents starvation-induced increases in specific binding of cortisol

Pottinger, T.; Brierley, I.. 1997 A putative cortisol receptor in the rainbow trout erythrocyte: stress prevents starvation-induced increases in specific binding of cortisol. Journal of Experimental Biology, 200 (14). 2035-2043.

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Binding sites for the steroid hormone cortisol, with characteristics typical of a steroid receptor, were detected in the rainbow trout erythrocyte. Binding of [3H]cortisol to a washed and purified erythrocyte suspension was saturable (Nmax = 0.33 ± 0.06 fmol/2.106 cells; ~100 ± 18 sites/cell;  ± SEM, n = 6), of high affinity (Kd = 4.6 ± 0.4 nmol l-1), and reversible in the presence of an excess of inert ligand. Maximum levels of specific binding were observed within 60 mins of the addition of [3H]cortisol at 4oC and were stable for 2 - 3 h. Within 20 mins of the addition of excess unlabelled ligand, 60% of specifically bound [3H]cortisol had dissociated. Both dexamethasone and cortisol completely displaced specifically-bound [3H]cortisol at 100-fold excess whereas a 1000-fold excess of unlabelled cortisone, 11-ketotestosterone, estradiol-17β, testosterone, and 17,20β-dihydroxy-4-pregnen-3-one failed to displace specifically bound [3H]cortisol. Specific binding sites for [3H]cortisol were located predominantly (92%) within the cytosolic fraction of the erythrocyte with a trace amount of specific binding (8%) detectable in the membrane fraction. No specific binding of [3H]cortisol was apparent in the erythrocyte nuclear fraction. A seven-day period of confinement stress resulted in no significant change in the number of erythrocyte cortisol-binding sites in rainbow trout, although plasma cortisol levels were significantly elevated in the stressed fish. However, in control unconfined fish there was a progressive and significant increase in the number of binding sites per cell during the course of the experiment (from 0.097 ± 0.030 to 0.260 ± 0.070 fmol/2.106 cells). A similar result was obtained when the experiment was repeated for confirmation. In both experiments food was witheld from control and confined fish because of the negative impact of stress on appetite. The possibility that the increase in erythrocyte cortisol-binding sites was related to the withdrawal of food was tested by quantifying the number of cortisol-binding sites in erythrocytes over a 14-day period in unstressed rainbow trout maintained on normal rations and in unstressed fish from which food was witheld. A significant increase in the number of cortisol-binding sites was observed with time in the fasted fish (from 0.33 ± 0.07 to 0.53 ± 0.03 fmol/2.106 cells). These data suggest that the abundance of erythrocyte cortisol binding-sites in trout is a function of nutritional status, and that stress opposes a fasting-induced increase in number of binding sites.

Item Type: Publication - Article
CEH Sections/Science Areas: _ Pre-2000 sections
ISSN: 0022-0949
Additional Information. Not used in RCUK Gateway to Research.: Click on the official URL to access freely available full text.
Additional Keywords: erythrocyte, cortisol, stress, receptor, starvation, rainbow trout, red blood cell
NORA Subject Terms: Zoology
Biology and Microbiology
Date made live: 28 Jul 2015 08:55 +0 (UTC)

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