§5.311 



BALANCE OF MONOVALENT ELECTROLYTES 



211 



in causing a marked increase in Cl~ uptake is similar to their action 

 on Na + , it cannot be assumed that the transport of chloride ions 

 follows passively upon that of sodium, since the rate of uptake of 

 the two ions through the skin has been shown to be independent. 



In the intact animal the secretion of the adrenal cortex may be 

 stimulated by adrenocorticotrophin ACTH, (§ 4.231), from the 

 adenohypophysis. 



The effect of Pituitrin, an extract in this case of the neuro- 

 hypophysis of a whale, on the sodium uptake of isolated skin 



Sodium filtered 



10 

 mequiv/kg/hr 



Fig. 5-13. Relationship between the percentage of the sodium 

 reabsorbed from the kidney tubules (ordinates) and the total 

 amount of sodium filtered through the glomeruli of the kidneys in 

 m.equiv/kg/hr (abscissae) in the bullfrog, Rana catesbiana. The 

 percentage is high over a wide range of concentrations of sodium 

 in the tubules (from Sawyer, 1956). 



(Fig. 5- 12c) seems anomalous. The Pituitrin used was believed to 

 be free of anterior lobe contamination, and therefore of ACTH, 

 but oxytocin and antidiuretic hormone, ADH*, were certainly 

 present in the extract and the latter caused so great a concurrent 

 uptake of water that, although the absolute amount of sodium was 

 increased as shown, the net effect was actually dilution (Sawyer, 

 1956). It would be curious, in view of the situation in other 

 vertebrates, if neurohypophysial hormones should aid the uptake 

 of salts in amphibians. 

 * = vasopressin. 



