碩士 / 國立海洋大學 / 食品科學系 / 88 / When tliapia (Oreochromis niloticus O. aureus) and grey mullet (Mugil cephalus) were exposed to acute toxicity concentration of 14~38 ppm cadmium (Cd), gill followed by liver accumulated the highest concentrations of Cd which increased as the exposure time and Cd concentration in water increased. Maximal accumulation reached when the fish were exposed to Cd for 50 h. Prolonged exposure from 50 to 90 h, Cd accumulation increased apparently in liver. Muscle and blood showed no significant increase in Cd.
Acute toxicity of 19, 28 and 38 ppm Cd caused conspicuous hematological anomalies in tilapia. Tilapia exposed to Cd for up to 49 h showed changes in white blood cell count (WBC), red blood cell count (RBC), hematocrit (Hct), hemoglobin (Hgb), and mean corpuscular hemoglobin concentrations (MCHC), all of which decreased apparently and erythrocytes become macrocytie after19 h.
In-vivo studies showed that lipoxygenases (LOX, E.C.1.13.11.12) of tilapia gill were induced to the highest activities when the fish were exposed to 28 ppm Cd for 19 h, or 19 ppm for 20 h, while 5-, and 12-LOX increased in activities and 15-LOX decreased. Gill 5-LOX of grey mullet was induced to the highest activity when the fish were exposed to 14 ppm Cd for 20 h, but activities of 12-, and 15-LOX induced to the highest after 50 h exposure. Dihydroxy- eicosatetraenoic acid (di-HETE) or leukotrienes (LTs) were detected in gill tissues of both tilapia and grey mullet.
In-vitro studies showed that Cd inhibited the tilapia gill LOX. Inhibitors of LOX, nordihydroguaiaretic acid and diphenyl sulfide inhibited 5-LOX-catalyzed arachidonate oxidation producing 5-hydroperoxyeicosatetraenoic acid (5-HpETE) and LT synthase-catalyzed 5-HpETE reaction producing LTs both in tilapia and grey mullet gill. It seemed that 5-LOX or LT synthase activities resided on a single protein in tilapia and grey mullet gill similar to the protein possessing both activities characterized from rat basophilic leukemia (RBL-1) cells.
Green tea extracts (GTE) obtained by refluxing for 90 min or by soaking in 100 oC hot water for 5 min, containing a dry weight of 47-57 ppm inhibited 5-, 12-, and 15-LOX activities of fish gill. The two extracts had similar inhibitory effects. GTE was found to scavenge active oxygen radical. Similar inhibitory effects were found on LOX of tilapia gill and grey mullet gill. GTE was a stronger inhibitor of the hemoglobin-catalyzed oxidation of linoleic acid than vitamin E. Mixing GTE with tilapia or grey mullet red blood cells in-vitro resulted in a blood thinning effect. The rheological data fit power-law model, =K n + C, where = shear stress, = shear rate, K = fluid consistency, n = flow behavior index. The addition of GTE reduced tilapia and grey mullet blood fluid consistency and caused a thinning consistency making the blood flow behavior becoming closer to Newtonian type.
These results suggest the antioxidants naturally occurring in green tea inhibited both hemoglobin-catalyzed oxidation of linoleic acid, and an inhibition of LOX activities in fish gill. Drinking of green tea may have preventive effect in blood thinning and atherosclerosis.
| Identifer | oai:union.ndltd.org:TW/088NTOU0253023 |
| Date | January 2000 |
| Creators | Liu, Yu-ju, 劉玉茹 |
| Contributors | Pan, Sun Bonnie, 孫寶年 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 86 |
Page generated in 0.0021 seconds