Review of data on the role of cortisol at the final stages of spawning migration and the reproductive cycle in sturgeons (Acipenseridae)

This review presents data on the role of cortisol (F) at the final stages of the reproductive cycle in migratory sturgeons (Acipenseridae) of the Volga-Caspian region: Russian sturgeon (Acipenser gueldenstaedtii Brandt et Ratzeburg, 1833), stellate sturgeon (Acipenser stellatus Pallas, 1771) and beluga (Huso huso (Linnaeus, 1758) obtained using a special variant of enzyme-linked immunosorbent assay (ELISA), which allowed us to compare the indicators of different years. The dynamics of F level in blood serum (BS) and the state of the interrenal gland (IG) in sturgeons were studied during feeding in the sea and at the beginning of the anadromous migration, as well as at the reproduction in the conditions of hatcheries. Higher levels of F in BS and high functional activity of IG are characteristic of sturgeon migrants when entering the river compared with data for fish during feeding in the sea. Reservation of sturgeon breeders at the hatchery led to decrease of the F serum level; and hormonal stimulation of maturation caused an increase in this indicator. Data on the F content in oocytes and abdominal (coelomic) fluid during maturation of female sturgeon are also presented. The F “profiles” were evaluated in sturgeon breeders under stress impacts that are unavoidable at the conditions of hatchery enterprises, as well as under experimentally simulated stress impacts. Peculiarities of the interaction of the hypothalamic-pituitary-gonadal and hypothalamic-pituitary-interrenal axes in sturgeons during reservation at hatcheries and during hormonal stimulation of fish maturation are discussed. Particular attention is paid to the compilation of data contained in the works performed in the late 90s – early 2000s under the guidance of Dr. Sc., prof. I.A. Barannikova (1926–2017), to whose memory the review is dedicated.

Morphometric Evaluation of Interrenal Gland and Kidney Macrophages Aggregates in Normal Healthy Rainbow Trout (Oncorhynchus mykiss) and after Bacterial Challenge withYersinia ruckeri

Macrophage aggregates (MA) occur in various organs of fish as discrete aggregations of pigmented macrophages. The study presented herein investigates the quantitative modifications from normal anatomical condition, of interrenal gland (IG) and kidney MA in six treatment groups of adult rainbow trout submitted to either specific or aspecific immune stimulation and subsequently challenged withYersinia ruckeri. Routinely stained tissue sections from both IG and kidney were analysed. The percentage of tissues occupied by MA and the MA density (number/mm2) were calculated on at least 10 randomly selected nonoverlapping fields taken from each tissue section. MA morphometric findings from challenged fish were compared to those from a control group. Results showed that fish from control group displayed a statistically significant (P<0.05) higher percentage of tissue occupied by MA and MA density. Among different treatment groups, anti-Yersinia ruckeriimmunized fish, which did not show clinical signs of disease after bacterial challenge, displayed higher values of morphometric parameters compared with symptomatic fish from other groups. Our study demonstrates that the quantification of the area occupied by MA might be an efficient parameter to evaluate the general condition of a salmonid population since it positively correlates with the health status and negatively with stress factor such as the acute bacterial infection.

Redefining the Initiation and Maintenance of Zebrafish Interrenal Steroidogenesis by Characterizing the Key Enzyme Cyp11a2

Zebrafish are emerging as a model to study steroid hormone action and associated disease. However, steroidogenesis in zebrafish is not well characterized. Mammalian P450 side-chain cleavage enzyme (CYP11A1) catalyzes the first step of steroidogenesis, the conversion of cholesterol to pregnenolone. Previous studies describe an essential role for zebrafish Cyp11a1 during early development. Cyp11a1 has been suggested to be the functional equivalent of mammalian CYP11A1 in the zebrafish interrenal gland (equivalent to the mammalian adrenal), gonad, and brain. However, reported cyp11a1 expression is inconsistent in zebrafish larvae, after active cortisol synthesis commences. Recently a duplicated cyp11a gene, cyp11a2, has been described, which shares an 85% identity with cyp11a1. We aimed to elucidate the specific role of the two cyp11a paralogs. cyp11a1 was expressed from 0 to 48 hours post-fertilization (hpf), whereas cyp11a2 expression started after the development of the interrenal primordium (32 hpf) and was the only paralog in larvae. cyp11a2 is expressed in adult steroidogenic tissues, such as the interrenal, gonads, and brain. In contrast, cyp11a1 was mainly restricted to the gonads. Antisense morpholino knockdown studies confirmed abnormal gastrulation in cyp11a1 morphants. cyp11a2 morphants showed impaired steroidogenesis and a phenotype indicative of metabolic abnormalities. The phenotype was rescued by pregnenolone replacement in cyp11a2 morphants. Thus, we conclude that cyp11a1 is required for early development, whereas cyp11a2 is essential for the initiation and maintenance of zebrafish interrenal steroidogenesis. Importantly, this study highlights the need for a comprehensive characterization of steroidogenesis in zebrafish prior to its implementation as a model organism in translational research of adrenal disease.