Elevation of plasma cortisol and hypertrophic response of inter‐renal and chromaffin tissues of rainbow trout, Oncorhynchus mykiss (Walbaum), to the harmful diatom Chaetoceros concavicornis

Abstract

Changes in plasma eortisol concentrations and inter-renal and chromaffin tissues of rainbow trout, Oncorhynehus mykiss (Walbaum), exposed to harmful concentrations of the diatom Chaetoceros eoncavicornis were investigated. The plasma cortisol level of trout exposed to C. eoncavicornis was over 10-fold greater than that of untreated trout. Computerassisted feulgen-microspectrophotometry was employed in order to assess the activity of inter-renal and chromaffin cells. The total areas of inter-renal and chromaffin nuclei in trout treated with C coneavicornis significantly inereased compared to those of untreated fish. In contrast, the chromatin density of inter-renal and chromaffin nuclei in treated trout decreased significantly. This decrease of chromatin density in treated fish was caused by an increase in the low-density components, and a decrease in the middle-density and high-density components. Although the hypertrophic changes to the inter-renal and chromaffin nuclei of treated fish exhibited the same general trend, the extents to which the changes took plaee were different, oecurring more rapidly within inter-renal tissues. The rainbow trout exposed to harmful concentrations of C. eoneavicornis were experieneing a severe physiological disturbance to which they tried to adapt.

Primary stress responses of common carp, <I>Cyprinus carpio</I>, exposed to copper toxicity

“…Along this axis corticotropin release factors (CRF) are given off from the hypothalamus during stress stimulating the secretion of the pituitary hormones as prolactin (PRL) and adrenocorticotropin (ACTH) (Fu et al 1990, Barton and Iwama 1991, Iwama et al 2003. In turn, ACTH stimulates the synthesis and release of cortisol, the major corticosteroid from the interrenal cells in fish (Yang and Albright 1995). The role of cortisol as an intermediary in metabolism is vital, since it is the major gulcocorticosteroid secreted by the teleosts' interrenal tissue in response to adrenocorticotropic hormone stimulation (Yang andAlbright 1995, Pottinger et al 2000).…”

“…In turn, ACTH stimulates the synthesis and release of cortisol, the major corticosteroid from the interrenal cells in fish (Yang and Albright 1995). The role of cortisol as an intermediary in metabolism is vital, since it is the major gulcocorticosteroid secreted by the teleosts' interrenal tissue in response to adrenocorticotropic hormone stimulation (Yang andAlbright 1995, Pottinger et al 2000). Indeed, increased PRL release has been implicated in the successful adaptation of fish to acidic water (Wendelaar Bonga et al 1984, 1987 and heavy metals (Fu et al 1990).…”