Factorial effects of salinity, dietary carbohydrate and moult cycle on digestive carbohydrases and hexokinases in Litopenaeus vannamei (Boone, 1931).
Litopenaeus vannamei were reared in close cycle over seven generations and tested for their capacity to digest starch and to metabolise glucose at different stages of the moulting cycle. After acclimation with 42.3% of carbohydrates (HCBH) or 2.3% carbohydrates (LCBH) diets and at high salinity (40 g kg(-1)) or low salinity (15 g kg(-1)), shrimp were sampled and hepatopancreas (HP) were stored. Total soluble protein in HP was affected by the interaction between salinity and moult stages (p<0.05). Specific activity of alpha-amylase ranged from 44 to 241 U mg protein(-1) and a significant interaction between salinity and moult stages was observed (p<0.05), resulting in highest values at stage C for low salinity (mean value 196.4 U mg protein(-1)), and at D0 in high salinity (mean value 175.7 U mg protein(-1)). Specific activity of alpha-glucosidase ranged between 0.09 and 0.63 U mg protein(-1), an interaction between dietary CBH and salinity was observed for the alpha-glucosidase (p<0.05) and highest mean value was found in low salinity-LCBH diet treatment (0.329 U mg protein(-1)). Hexokinase specific activity (range 9-113 mU mg protein(-1)) showed no significant differences when measured at 5 mM glucose (p>0.05). Total hexokinase specific activity (range 17-215 mU mg protein(-1)) showed a significant interaction between dietary CBH and salinity (p<0.05) with highest value (mean value 78.5 mU mg protein(-1)) found in HCBH-high salinity treatment, whereas in the other treatments the activity was not significantly different (mean value 35.93 mU mg protein(-1)). A synergistic effect of dietary CBH, salinity and moult stages over hexokinase IV-like specific activity was also observed (p<0.05). As result of this interaction, the highest value (135.5+/-81 mU mg protein(-1)) was observed in HCBH, high salinity at D0 moult stage. Digestive enzymes activity is enhanced in the presence of high starch diet (HCBH) and hexokinase can be induced at certain moulting stages under the influence of blood glucose level. Perspectives are opened to add more carbohydrates in a growing diet, exemplifying the potential approach for less-polluting feed.
Gaxiola
Gabriela
G
Unidad de Docencia e Investigación de Sisal, Facultad de Ciencias, UNAM, Puerto de Abrigo, Sisal, Yucatán, cp 97000, México. mggc@hp.fciencias.unam.mx
Cuzon
Gerard
G
García
Tomás
T
Taboada
Gabriel
G
Brito
Roberto
R
Chimal
María Eugenia
ME
Paredes
Adriana
A
Soto
Luis
L
Rosas
Carlos
C
van Wormhoudt
Alain
A
D000818:Animals; D004040:Dietary Carbohydrates / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D006026:Glycoside Hydrolases / Q000378:metabolism*; D043143:Hepatopancreas / Q000737:chemistry / Q000201:enzymology / Q000378:metabolism; D006593:Hexokinase / Q000378:metabolism*; D018978:Molting / Q000502:physiology; D033561:Penaeidae / Q000201:enzymology* / Q000254:growth & development / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology*; D013213:Starch / Q000378:metabolism; D001617:beta-Glucosidase / Q000378:metabolism
D004040:Dietary Carbohydrates; D012965:Sodium Chloride; D013213:Starch; D006593:Hexokinase; D006026:Glycoside Hydrolases; C019822:carbohydrase; D001617:beta-Glucosidase; D005947:Glucose