The hexokinase reaction in tissue extracts from normal and diabetic rats.

The recent papers by Cori and his coworkers have stimulated interest in the hexokinase reaction in tissue extracts from normal and pathological animals. Our interpretation of this work pertinent to the subject of this paper is as follows: (1) Rats injected with alloxan yield muscle extracts which show an initial lag of hexokinase activity of 10 to 15 minutes duration, owing t,o the presence in muscle from diabetic animals of a labile inhibitory factor from the pituitary gland (1). (2) Th e initial slow phase in muscle extracts from alloxanized rats is abolished by the prior addition of insulin (2). (3) The addition of Upjohn’s adrenal cortical extract (ACE) to muscle extracts from alloxanized rats often markedly intensifies the initial slow phase of the hexokinase reaction. This is presumed to be caused by an intensification of the inhibitory action of the pituitary factor present in diabetic tissue. This added effect, of adrenal cortical hormone is always prevented by the prior addition of insulin (2, 3). (4) Muscle extracts from alloxanized animals subject to mild aging (45 to 270 minutes at 0’) are not affected by the addition of ACE. The hexokinase reaction is similar in rate to that obtained with fresh extracts in the presence of insulin. Presumably a labile factor is lost during the aging process; in this respect it resembles a factor present in preparations from the anterior pituitary gland (3). (5) In a series of thirty rats given alloxan, and considered to be diabetic, fifteen yielded muscle extracts which, in the presence of ACE, gave rates of the hexokinase reaction which ranged from 24 to 79 per cent of those obtained with the same extracts in the presence of ACE + insulin. These decreases of hexokinase rate were considered significant (3). We report in this paper similar experiments on tissue extracts from normal rats and alloxanized rats. Methods