In the glucose tolerance test (GTT) and insulin glucose tolerance test (IGTT) with fish, the change of blood sugar content is determined by a repeated bleeding method or a one-time bleeding method. It is desirable that the change of blood sugar is found through samples of blood taken repeatedly at regular intervals from a given fish. It is to be expected that the blood sugar will increase in proportion to the rapid shock caused by handling and repeated bleeding. The present study, therefore, w as carried out to determine the influence of repeated bleeding and anesthetization on the change of blood sugar content of the red sea bream (Chrysophrys major), to determine the difference of influences among anesthetics, and to compare the change of blood sugar content in the GTT and IGTT which was obtained by a repeated bleeding method and that obtained by a one-time bleeding method. The results obtained can be summarized as follows: 1) The blood sugar content of the red sea b ream determined by repeated bleeding without anesthetization increased remarkably each time a bleeding was taken, and there was a large difference between the change of blood suger content in individual fish. 2) The increase of blood sugar obtained by repeated bleeding on a given fish anesthetized with urethane (5,000 ppm), or quinaldine (20 ppm), or MS-222 (100 ppm) was lower than that obtained by repeated bleeding without anesthetization. The increase of blood sugar obtained by repeated bleeding with MS-222 anesthetization was the least. 3) The average blood sugar content obtained from three different fish at each t ime by the one-time bleeding method with urethane anesthetization was always in the range from 50-75 mg/dl. 4) The changes of blood sugar content in the GTT and IGTT obtained from a given fish by repeated bleeding with MS-222 anesthetization showed the same curve as those obtained from numerous fish by a one-time bleeding method with urethane anesthetization, but the quantities of increase and decrease of blood sugar content obtained by both methods were different.同一個体より反復採血した場合のマダイの血糖変動,その血糖変動に対する麻酔の影響,麻酔剤の種類による影響の違い,同一魚体より反復採血して求めた血糖変動と多数魚体からそれぞれ1回採血して求めた値を集積してえた血糖変動との異同について検討し,次の結果を得た. 1. 麻酔しない同一魚体から反復採血すると,採血回数が増すにしたがつて血糖が著しく増加した.また血糖上昇に大きな個体差が認められた. 2. Urethane(5000ppm),Quinaldine(20ppm)およびMS-222(100ppm)で麻酔した同一魚体より反復採血した場合の血糖増加は,麻酔しないで反復採血した場合のそれよりかなり小さかつた.特にMS-222で麻酔し反復採血した場合の血糖上昇はゆるやかであつた. 3. 各測定時にUrethaneで麻酔した3個体からそれぞれ1回採血して求めた平均血糖値は,常に50～75mg/dlの範囲にあり,ほとんど一定の値を示した. 4. MS-222で麻酔し,同一魚体から反復採血して求めたグルコースあるいはインシュリン・グルコース負荷後の血糖変動は,多数個体のそれぞれから1回採血して求めた負荷後の血糖変動と同じ傾向を示したが,その血糖の上昇程度あるいは降下程度にかなりの差が認められた
