238 



Colchicine 



markablc result is found when colchicine is injected into animals 

 after one renal artery has been ligated.^^ Yhe ischemic kidney shows 

 a considerable number of mitoses, mainly in the excretory (Schweig- 

 ger-Seidel) tubules and the pelvis (Fig. 9.11). Similar facts have 

 been observed in kidneys made partly ischemic by the endocrine 

 kidney operation of Selye.^^ The following experiments were aimed 



TABLE 9.8 

 Mitotic Index in the Remaining Kidney of Adult Rats Injected With Colchicine 



(After Carnot and May^^ 



at finding the possible nature of the mitotic stimulus.^! The number 

 of renal mitoses after nephrectomy was decreased by injections of 

 thiouracil, a drug which depresses thyroid function. Thyroidectomy, 

 however, did not prevent or retard the increase of size of the re- 

 maining kidney in the rat.^^ Thyroxin was nevertheless found to 

 stimulate renal mitoses as much as woidd a nephrectomy. When 

 this was carried on and thyroxin injected afterwards, the mitotic 

 increase was greater than expected, lliis may indicate a truly syner- 

 gic action of the two stimuli. Ihe differences in body weight be- 

 tween controls (nephrectomy alone) and the other rats, and the 

 fact that the mitotic counts were corrected for 100 g. of body weight, 

 make these results difficult to interpret and suggests the need for 

 further research (Table 9.9) . 



The hypothesis which was put forward following these data was 

 that thyroxin did not act directly on renal tissue, but that the in- 

 creased jMotein catabolism resulting from the action of the hormone 

 provided the factor responsible for mitosis.^^ Some substance present 

 in the urine may be suspected since, as mentioned above, ligature of 

 the ureter promotes cell division (Fig. 9.10). However, such mitotic 

 activity is mainly located in the connective tissue of the kidney. An 

 important fact is that unilateral ureter ligation promotes mitosis in 



