922 7. MERCURIALS 



in the convoluted segments. With low doses (2.5 mg/kg), disappearance of 

 SH groups was observed only in the terminal portion of the proximal tu- 

 bules and the ascending loops, the latter being the most sensitive region 

 of the nephron. Time studies showed that the terminal proximal tubules 

 are affected first and up to 1 hr show more reduction than the loops of 

 Henle. Incubation of kidney sections with 20 mM mersalyl (Cafruny et al., 

 1955 b) or saturated HgClg (Cafruny et al., 1955 a) produces marked non- 

 specific reduction in free SH groups, indicating that the pattern seen in the 

 whole animal is due in part to the factors involved in the resorption and 

 secretion of the mercurials. Cafnmy and Farah (1956) later used dogs so 

 that correlation between diuresis and SH group disappearance might be 

 made. Kidneys were removed at the peak of diuresis (around 90 min) from 

 10 mg/kg of mersalyl, urine flow and Na+ being increased 5- to 6-fold, and 

 the changes given in the accompanying tabulation were observed, indicat- 



ing that selective reaction with SH groups in certain regions of the kidney 

 does occur. It should be pointed out that the nature of these SH groups is 

 not known; they may be on enzymes, carriers, or nonfunctional proteins. 

 Farah and Kruse (1960) used seven mercurials at 4 mg Hg/kg in rats 

 and found moderate reduction of the protein SH groups (around 20-30%) 

 in the terminal proximal tubules, the loops of Henle, and the collecting 

 ducts, and it was concluded that maximal diuresis occurs when 20% of the 

 protein SH groups of the proximal tubule are reacted, and thus that no 

 more than this can be related to the diuresis. However, there is no correla- 

 tion between diuresis and decrease in the SH groups, since p-MB and MM, 

 both nondiuretic, produce similar changes in these groups. HgClg and mer- 

 salyl at equimolar doses cause comparable decreases in renal SH groups in 

 rats, and this was noted particularly at the bases of the proximal tubular 

 cells (Gayer and Partowi, 1962). Renal S — S groups do not change for sev- 

 eral hours after injections of HgClg or chlormerodrin, but from 6 to 24 hr 

 there is a,n increase in S — S groups at the expense of SH groups (Shore and 

 Shore, 1962). This may be related to the potent inhibition of protein disul- 

 fide reductase, but is probably not correlated with diuresis since it occurs 



