VOL. 12 (1953) 



EFFECTS OF INSULIN ON MELANOMA 



341 



The influence of insulin on aerobic metabolism 



Whenever insulin stimulated in vitro anaerobic acid production by S-91 melanoma 

 slices, it was found that the (^co was also increased if this was measured. Inorganic zinc 

 alone, on the other hand, did not stimulate aerobic acid formation. Contrary to in vitro 

 results secured with certain normal tissues insulin never increased the Qo^, and in fact 

 sometimes decreased it (o to ca. 25%). 



In spite of the absence of respiratory stimulation, insulin frequently increased the 

 absolute Pasteur effect ((^co - ^coJ' °^ depression of net acid formation due to the 

 presence of O2 (Table V, Fig. 6), and in no case was the absolute Pasteur effect signifi- 

 cantly decreased by insulin. 



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+40 



+30 



+20 



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 «5 



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-20- 



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 ce 



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rZn 



Fig 6. Comparison of 3 different patterns of response of S-gi melanoma slices to insulin. Each bar 

 represents the percentage stimulation or inhibition relative to the control (minus insulin). A, with 4 

 units of crystalline zinc-insulin per ml (from data of Table VI); B, with 4 units of amorphous low- 

 zinc insulin plus i.i y zinc per ml (one experiment involving pooled slices from 3 tumors of the same 

 transplant series pre-heated at 40° C for 16 hours); and C, with 4 units of crystalline zinc-insulin 

 per ml (from average data of 3 experiments. Results obtained with i.i y of inorganic zinc per ml 

 (without added insulin) are shown to the right of C. All experiments with 0.625 % dextrose, 0.03 M 



KHCO, 



95% 



N„ 



and 5 % CO, 



There are numerous reports^- 1"*- ^^ that insulin administration to tissue slices in vitro 

 raises the R.Q- This effect was obtained in melanoma, but to a variable extent. Table VI 

 shows that this elevation of R.Q. can occur without concomitant increase in mano- 

 metrically measurable acid formation, and that the effect is attributable to insulin 

 rather than to zinc per se. This is further borne out by similar results obtained with low- 

 zinc insulin in the absence of added zinc. The general range of responses observed, in 

 terms of per cent stimulation or inhibition, under both aerobic and anaerobic conditions 

 is illustrated in Fig. 6. 



References p. 346. 



