WE have endeavoured to determine the relationship between temperature and destruction of sterile watery buffered solutions of insulin (about 15 international units per mg.) and to find a mathematical expression for it. According to the law of mass action we might expect that the rate at which insulin is destroyed at a constant temperature at any moment should be proportional to its concentration as expressed by the well-known equation k=t.log aa k= where k is the velocity constant, a the initial concentration, and x the aaount destroyed at the time t. This expression can be used to evaluate k, the quantity (a -x) left at a given time t being estimated by biological standardisation.
It seems very probable that insulin having been found in extracts from molluscs (1) and plants (2a, b and c) as well as in the pancreas of vertebrates may exist in all the invertebrates and one way of attacking this problem is to study the effect of insulin injection on the blood sugar of suitable invertebrate animals. Acting on a suggestion by Prof. A. Krogh I have therefore made a number of such injections and as a preliminary I give in this paper my results regarding the normal content of sugar and other reducing substances in the animals employed.In table1 I have given the total reducing power expressed as glucose per cent of a number of specimens of butterfly larvae and pupae and the crayfish. The blood samples have been obtained by cutting or pricking one of the pro-legs of the larvae, the head of the pupae and one of the thoracal legs of the crayfish. The analyses have been made by the method of Hagedorn(3) (on 0.1 ccm samples when nothing else is stated).It is seen that the percentage of reducing substance is not nearly so constant as is the case in warm blooded animals but may vary considerably and it seems natural to suppose that in these animals the blood sugar level may be dependent on the state of nutrition. To study this possibility some larvae were starved for a certain period and then examined again. The animals were placed at 28O during the period of starvation except Smerinthus which \\-as placed at room temperature. In table 2 I have given'the results.Der Redaktion am 9. Februar 1924 zugegangen.
According to previous publications from this laboratory ( H e mm i n g s e n , 1933, p. 198 and 208; H e m m i n g s e n and Weitze, 1936, p. 628), the accuracy to be obtained in single insulin assays involving abt. 100-160 mice with a body weight dispersion of 4 g, corresponded to a standard deviation varying from abt. I 2 to abt. 25 p. c. of the average.Unsuccessful attemps at improving the accuracy of the convulsive dose method have been published for tiny fishes ( H e m m i n gs e n and B r u u n , 1938) and adrenalectomized rats and mice ( H e mm i n g s e n , N i e l s e n and L e v i n N i e l s e n , 1938).As reported by H e m m i n g s e n and M a r k s (1933, p. 88-89) the mortality of mice during the experiment and on the day following the experiment is I 9. I p. c. when the tests are carried out at 37O C against I 2.4 p. c. when they are carried out at 290 C. According to K r o g h and H e m m i n g s e n ( 1 9 2 6 ) and T e t e n s N i e l s e n (1938) it is possible to observe marked symptoms of the injected insulin also at somewhat lower temperatures; and they state that the reduction of body temperature and the resulting lower metabolic activity protects the mice against the lethal effects of insulin.Experiments at lower temperatures might thus be expected to entail a smaller rate of mortality. In addition, an experimental temperature nearer to the environmental temperature obtaining between the experiments might tend to protect the mice against catching colds, which often disturb experiments at 29" C and are probably largely responsible for the high mortality.
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