Effects of estradiol on fatty acid composition and tissue structure of hepatopancreas in Macrobrachium nipponense

Field: Agricultural and Biological Sciences (Life Sciences)

Estradiol is an important sex hormone for ovary development in vertebrate. Many reports have showed that estradiol can not only be found in crustacean,but also be involved in their ovary development.The level of estradiol is related with ovary development in hepatopancreas of Macrobrachium nipponense. And hepatopancreas is the main nutritional resource providing fatty acids for ovary development. And fatty acid contents in ovary change with ovary maturation in M. nipponense. The effects of estradiol on fatty acid composition and tissue structure of hepatopancreas in M. nipponense were investigated via injecting prawns with 5,0. 5,0. 05 μg estradiol per g by body weight once every 5 days for 2 times. The control group was injected with water. Each group had three parallels. Hepatopancreas was sampled on the 10 th day.Fatty acids were extracted by FOLCH method and measured by GC-MS. Results showed that the main fatty acids in hepatopancreas of M. nipponense were C16: 0,C18: n7 and C18: 2n,which meant that they were the main energy sources in hepatopancreas of M. nipponense. Multi-unsaturated fat acids( MUFA) and poly-unsaturated fat acids( PUFA) in hepatopancreas of M. nipponense were 39. 05 ± 1. 16% and 42. 71 ±2. 56%,respectively. Total contents of saturated and monounsaturated fatty acids were up-regulated by 5,0. 05 μg·g- 1estradiol,while they were down-regulated by 0. 5 μg·g- 1estradiol. And the contents of C18∶ n7 and C18∶ 2n in 0. 05 μg·g- 1and 5 μg·g- 1groups showed no significant difference with the control group( P 0. 05) while they were down-regulated significantly by 0. 5 μg·g- 1estradiol( P 0. 05). And reports showed that they increased during ovary development in M. nipponense. Estradiol also significantly affected the contents of C18∶ 3n6,C18∶ 4n,C20∶ 4n6,C20∶ 5n3,C22∶ 4n6 and C22∶ 5n3. And 5,0. 05 μg·g- 1estradiol significantly down-regulated PUFA contents( P 0. 05),especially C18∶ 4n,C20∶ 5n3,C22∶ 4n6 and C22∶ 5n3( P 0. 05) while 0. 5 μg·g- 1estradiol significantly up-regulated MUFA contents( P 0. 05),especially C18∶ 3n6,C18∶ 4n,C20 ∶ 4n6,C20 ∶ 5n3( EPA),C22 ∶ 4n6 and C22 ∶ 5n3( P 0. 05).And during the ovary development C20∶ 2n increased while C18 ∶ 3n and C20 ∶ 4n decreased,however C18 ∶4n,C22∶ 4n6 and C22∶ 5n3 weren't found in the ovary. Results showed 0. 5 μg·g- 1estradiol decreased the essential fatty acids for ovary maturation in hepatopancreas. The decreased fatty acids may be transported to the ovary from hepatopancreas.Histological section results showed that there were restzellen cell( RC),blasenzellen cell( BC),fibrillenzellen cell( FC) and embryonalzellen cell( EC) in hepatopancreas. BC and RC were dominant while FC and EC were fewer. And estradiol enlarged and increased BC,decreased RC in the hepatopancreas,with the biggest impact at 0. 5 μg · g- 1. Reports showed that numbers of BC and RC,in hepatopancreas of crustaceans changed with environment. RC could be transformed to BC when RC absorbed fragments,such as fat,metal. And RC could transport the fragments to proximal tubule. In this experiment,fatty acids upregulated by estradiol were probably transformed by RC to BC,resulting in BC being enlarged and vacuolate.