THE DIURETIC-ANTIDIURETIC ACTIVITY OF POSTERIOR PITUITARY EXTRACTS

¹ From the Pharmacology Laboratory, University of Michigan Medical School, Ann Arbor

1. When groups of mice, kept under as nearly uniform conditions as possible, are given the same amount of water per gram of body weight intraperitoneally, the urine excreted in the 3-hour period subsequent to injection varies widely in amount. The curve expressing the distribution of this variation is the S-shaped curve of continuous variability, similar to that described by Trevan for the dosage-mortality relationship of digitalis in frogs.

2. When such groups of mice are injected simultaneously with small amounts of pituitary extract the position of such a curve is altered, and the degree of alteration is somewhat proportional to the dosage of pituitary injected.

3. If, however, large doses are used, the effect may be reversed, in that large doses may be less effective than smaller ones, or stated differently, may be diuretic in relation to the effect of small doses.

4. The relative diuretic effect of large doses is associated with an increase in the absolute amount of chlorides, the concentration, however, remaining relatively constant after a value of about 1 per cent (1.8 per cent NaCl) is reached.

5. In the range in which there is a direct relation between dosage and inhibitory effect, it is possible to use the procedure described for the comparison of the antidiuretic activity of different pituitary preparations.