Evaluation Of Metallothionein-Ⅲ Gene Expression Levels In Different Brain Regions In Sheep Managed At Different Altitudes

The objectives of this experiment were to compare MT-III gene expression invarious brain tissues between Tibetan sheep managed at different altitudes andbetween Tibetan and Lanzhou Fat-tailed sheep managed at the same altitude and tocompare MT-III expression in various brain tissues in Gansu Alpine Merino sheep.Six Tibetan sheep (30-36mo) were randomly selected from Tibetan sheep flocks inHenan County, Qinghai (altitude3800m), and four Lanzhou Fat-tailed sheep inLintao County, Gansu (altitude1600m) were selected for sampling. Three Tibetansheep were transported to Lintao County and were managed with the LanzhouFat-tailed sheep for18mo before harvest. The remaining3Tibetan sheep weremanaged in Qinghai until harvest. For comparisons of MT-III activity in differentbrain regions in Gansu Alpine Merino, six lambs (4~5months) were randomlyselected from Gansu Alpine Merino flocks in Sunan County, Gansu (altitude3600m).Brain regions sampled post-harvest included the frontal lobe, temporal lobe, parietallobe, occipital lobe, pons, medulla, cerebellum, mesencephalon, pineal gland andhypophysis. Relative expression levels of MT-III gene in these tissues were analyzedby real-time PCR. The results were as follows:1. MT-III existed in all different regions of the brain (frontal lobe, temporal lobe,parietal lobe, occipital lobe, pons, medulla, cerebellum, mesencephalon, pinealgland and hypophysis) in all sheep. Gene expression was greatest in the pinealgland and least in the cerebellum (P <0.05).2. In sheep managed in their native environment, MT-III gene expression differedamong different regions of the brain (P<0.05) and the pattern of differencesamong regions of the brain was similar among the breeds (Tibetan, LanzhouFat-tail, Gansu Alpine Merino). Relative expression for the MT-III gene, fromhigh to low, was observed as follows: pineal gland, parietal lobe, frontal lobes,hypophysis, mesencephalon, occipital lobe, temporal lobe, pons, medulla andcerebellum. However, Tibetan sheep managed at Lintao County, Gansu (altitude 1600m) generally did not have different MT-III expression in different regions ofthe brain (P>0.05). At lower altitudes, it is possible that the difference in oxygenlevels resulted in different brain metabolism in Tibetan sheep, decreasing MT-IIIexpression. With the exception, of the difference in MT-III activity between thepineal gland and cerebellum, this resulted in similar MT-III expression amongbrain regions in the Tibetan sheep managed in a non-native environment.3. At3800m, the relative expressions of MT-III gene in the frontal lobe, temporallobe, parietal lobe, pons, medulla, mesencephalon and hypophysis in Tibetansheep were higher than those of Tibetan sheep at1600m (P<0.05). Altitudedifferences in Tibetan sheep for other brain regions were small, perhaps due todifferences in response to oxygen and sun radiation levels for these brain regions.4. The relative expression levels of MT-III gene was similar in Tibetan sheep andLanzhou fat-tailed sheep at1600m.