Abstract
For studies on the physiological functions of proteoglycan (PG) in salmon nasal cartilage for humans, it is important to clarify the qualitative and quantitative differences in PG contained in nasal cartilage among different types of salmon and among the locations of cartilage in the salmon head. In this study, as an alternative source of PG, we selected ‘Kaikyo salmon’ head cartilage. ‘Kaikyo salmon’ is rainbow trout that is farmed in the Tsugaru channel. We divided the head cartilage into 4 regions (those collected from the region around the brain, frontal head, upper region of the jaw, and tip of the nose and around the eyes), and investigated the PG content and molecular weight distribution of each cartilage. Among the 4 regions, the cartilage contents of the region around the brain and nasal tip and around the eye accounted for 33 and 32% of the total cartilage content, respectively, and were greater than those of the frontal head (20%) and upper region of the jaw (15%). However, the uronic acid content per g cartilage wet weight (representing the PG content) was 17.6-21.8mg and the protein content was 15.9-18.9mg in the 4 regions, showing no marked differences among them. In addition, no difference was noted in the molecular weight distribution of PG contained in the hot water extracts of cartilage among the regions, and 20-30% of the total PG was distributed in the high molecular weight region (5000000 or higher), similar to the distribution of a hot water extract of salmon nasal cartilage. These findings suggest that cartilage in the Kaikyo salmon head can be used as a substitute for the nasal cartilage of wild salmon. The raw materials for PG can be stably supplied using farmed fish, and the use of the head, a previously unused resource, may significantly contribute to the revitalization of the local industry.
