ヤツメウナギ消化管の脂質及びVitamin A

Abstract

In the adult lamprey, Entosphenus japonicus MARTENS, the potency of vitamin A is found at a very high level in various parts of the body. Among these parts, the alimentary canal, despite it weighing only one per cent of the body, contains the largest or nearly one half of the total vitamin A in the body as reported by Higashi et al. Curious to know why such a large amount of vitamin A is concentrated in that organ, the author assessed the oil and vitamin A in the tissue as well as the contents of alimentary canal and obtained the following results: 1. Vitamin A in the alimentary canal oil was determined at the levels of 614, 000 and 1, 150.000 I. U. per gram on the sample materials I and II of the mature fish which were caught in a spawning stream of Yamagata Prefecture in February and May 1958, respectively. Perhaps the latter value is the highest of vitamin A ever known on any natural materials. The calculation showed vitamin A of 42, 000 and 327, 000 I. U. per gram of the tissue on the samples I and II. The vitamin A concentration in the alimentary canal contents was assessed at a level much lower than of the tissue (Table 1). 2. A greater part of the vitamin A was found in the ester form with the amount of free form larger in sample II than sample I (Table 3). 3. Nearly 75 per cent of unsaponifiable matter of the alimentary canal tissue consisted of vitamin A, indicating a unique character that has never been observed in vitamin oils from any other species of fish. On the other hand, the unsaponifiable matter in the alimentary canal contents revealed little vitamin A but much sterols (Table 2). 4. A postulation explaining high concentration of vitamin A in the alimentary canal of the lamprey is proposed as follows: When the lamprey return to the fresh water for spawning, they seem to consume more fat and protein than vitamin A which have been stored abundantly in various parts of the body during their sea life. In consequence a portion of vitamin A which becomes exceedingly high beyond a limit acceptable to the tissues of the other organs and muscle, will be transported from these parts to the alimentary canal tissue and then excreted from the tissue to the inside of the canal. In other words, most of vitamin A of the alimentary canal contents do not seem to be the remains of food but those excreted from the canal.