Seasonal changes in hepatocytic lipid droplets, glycogen deposits, and rough endoplasmic reticulum along the natural breeding cycle of female ohrid trout (Salmo letnicaKar.)-A semiquantitative ultrastructural study

Sex-steroids and hypolipidemic chemicals impacts on brown trout lipid and peroxisome signaling - Molecular, biochemical and morphological insights

Lipid metabolism involves complex pathways, which are regulated in a similar way across vertebrates. Hormonal and hypolipidemic deregulations cause lipid imbalance from fish to humans, but the underlying mechanisms are far from understood. This study explores the potential of using juvenile brown trout to evaluate the in vivo interferences caused by estrogenic (17α-ethinylestradiol - EE2), androgenic (testosterone - T), and hypolipidemic (clofibrate - CLF) compounds in lipidic and/or peroxisomal pathways. Studied endpoints were from blood/plasma biochemistry, plasma fatty acid profile, ultrastructure of hepatocytes and abundance of their peroxisomes to mRNA expression in the liver. Both T and CLF caused minimal effects when compared to EE2. Estrogenized fish had significantly higher hepatosomatic indexes, increased triglycerides and very-low density lipoproteins (VLDL) in plasma, compared with solvent control. Morphologically, EE2 fish showed increased lipid droplets in hepatocytes, and EE2 and T reduced volume density of peroxisomes in relation to the hepatic parenchyma. Polyunsaturated fatty acids (PUFA) in plasma, namely n-3 PUFA, increased with EE2. EE2 animals had increased mRNA levels of vitellogenin A (VtgA), estrogen receptor alpha (ERα), peroxisome proliferator-activated receptor alpha (PPARα), PPARαBa and acyl-CoA long chain synthetase 1 (Acsl1), while ERβ-1, acyl-CoA oxidase 1-3I (Acox1-3I), Acox3, PPARγ, catalase (Cat), urate oxidase (Uox), fatty acid binding protein 1 (Fabp1) and apolipoprotein AI (ApoAI) were down-regulated. In summary, in vivo EE2 exposure altered lipid metabolism and peroxisome dynamics in brown trout, namely by changing the mRNA levels of several genes. Our model can be used to study possible organism-level impacts, viz. in gonadogenesis.

Oogenesis is accompanied by cyclic morphological changes in hepatocytes of Neotropical freshwater fish Piabina argentea

We determined for the first time the reproductive biology of Piabina argentea through macroscopic and microscopic analysis of ovaries and evaluated the morphological changes in hepatocytes. Two hundred and 46 specimens were collected, 204 females and 42 males, between March 2014 and February 2015. Biometrics data were obtained. From females, gonad and liver samples were conducted to histological, histochemical and immunohistochemical techniques. Mature ovaries were used to determine absolute and relative fecundity. Total length and body weight values indicated that females were larger than males. The estimated weight-length ratio showed negative allometric growth. The absolute fecundity average was 171.83 ± 59.89 oocytes per ovary. In addition, females spawning capable and regressing stages were found throughout the sampling period and the presence of all oocyte types in regressing stage ovaries indicated asynchronous oocyte development and multiple spawning. From regenerating to spawning capable stage the oocytes accumulated yolk in cytoplasm became bigger. While in the liver hepatocytes with a larger cell area during regenerating stage and proliferative activity in the spawning capable stage were observed. Thus, our results indicate that P. argentea had an opportunistic reproductive strategy and cyclic morphological changes of hepatocytes occurred during the oogenesis.