THE PITUITARY BODY 



reabsorption of water is masked and no clear-cut polyuria and 

 polydipsia occur. A view favored by many is that the thyro- 

 tropic hormone, by its indirect effect on the thyroid, is chiefly 

 responsible for the maintenance of a normal rate of glomer- 

 ular filtration.- In the pages which follow the evidence in 

 favor of the hypothesis just outlined as well as some observa- 

 tions to the contrary will be reviewed. Some of the best ob- 

 servations have been reported only recently and are impressive 

 because of the care with which they have usually been made. 

 I . The secretion of the vasopressor principle as a means of 

 preventing dangerous loss of body water. — Oilman and Good- 

 man (1936-37) performed a series of interesting experiments 

 in rats. They found that, if water and food were withdrawn 

 from normal rats, the rate of secretion of the urine, of course, 

 fell, depending upon the period of thirst. At the same time 

 diuresis-inhibiting effects, analogous to those produced by 

 pars neuralis extracts, could be secured by injecting suitably 

 prepared urine. The amount of diuresis-inhibiting principle 

 present increased as the period of water withdrawal was pro- 

 longed, so that the equivalent of as much as 5 units of hor- 

 mone was excreted by 20 rats during a period of 72 hours 

 without water. ^ No detectable amounts of the principle 

 could be discovered in the urine of rats drinking water ad 

 libitum. If rats were hypophysectomized and then subjected 

 to water-withdrawal, they secreted three times as much urine 

 as normal rats treated similarly; no diuresis-inhibiting hor- 

 mone could be found in their urine. Control experiments in- 

 dicated that the procedure used was suitable for identifying 

 diuresis-inhibiting (vasopressor) hormone. Moreover, the 

 diuresis-inhibiting substance in the urine of rats receiving 



^ Another possibility, in favor of which there is little evidence, is that a secretion 

 of the pars glandularis has diuretic effects not mediated through another gland of 

 internal secretion. White and Heinbecker suggested that a secretion of the thyroid 

 sensitizes the animal toward an anterior pituitary diuretic factor. 



3 Diuresis caused by the administration of a solution of NaCl to rats from which 

 water was withheld likewise was characterized by the rapid appearance of diuresis- 

 inhibiting principle in the urine. 



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