Hypernatraemia and Hyponatraemia 53 



Effect of potassium chloride 



In view of Laragh's (1954) findings of a rise in plasma [Na] 

 with the administration of potassium chloride in patients with 

 hyponatraemia, we gave 100 m-equiv. of potassium chloride 

 on two successive days to both the patients. There was no 

 increase in the plasma [Na] and only a slight rise in the plasma 

 [K]. 



The data so far reported show that the renal excretion of 

 sodium could be made to vary from very small to very large 

 amounts, and, in particular, although sodium continued to be 

 excreted while the plasma concentration was low, the kidneys 

 were able to conserve sodium during the dehydration reaction. 

 But a rise in the plasma [Na] produced by hypertonic saline 

 was followed by retention of water which restored the osmo- 

 lality of the plasma to its original level. 



Effect of pitressin 



All these results might be taken to show that these patients 

 had an intact antidiuretic mechanism which operated to 

 maintain their plasma osmolality at a lower level than normal. 

 Their response, however, to exogenous ADH given as pitressin 

 was quite unexpected. 



After one litre of water by intragastric drip the patients 

 received 100 m-u. of pitressin intravenously and 5 i.u. of 

 pitressin in oil intramuscularly. Urine was collected in hourly 

 periods for the following five hours; the gastric drip was 

 running throughout, but the amounts given after the initial 

 load were unfortunately not recorded. The results are shown 

 in Table III. In Fig. 2 they are compared with the results of 

 water deprivation. Ivor began with a concentrated urine, 

 but after the first hour the maximum osmolality achieved 

 after pitressin was some 500 or 600 m-osm. less than after 

 dehydration. The effect of pitressin was tested a second time 

 in Albert, and he then passed urine with a concentration of 

 215 m-osm. /I., that is, lower even than his own hypotonic 

 plasma. The low concentration of urine in these tests de- 

 pended on the comparatively high urine flow, and not on a 



