VOL. 12 (1953) 



EFFECTS OF INSULIN ON MELANOMA 



333 



increase of 110% (range 82 to 148%) over and above that caused by phenol alone. The 

 combined effects of magnesium and phenol are more completely illustrated in Fig. i 

 where the source of phenol was a commercial insulin preparation. 



The stimulating action of phenol on (2c6. o^ brain slices occurred only when it was 

 added before the tissue had been incubated at 38° C. A delay of 20 minutes at 38° C 

 before tipping the phenol was sufficient to eliminate the effect. Tissue exposed to 

 commercial insulin preparations (plus phenol), and then rinsed once in insulin-phenol- 

 free medium, behaved like untreated tissue both with respect to low (Jco^ ^" ^^^ absence 

 of these substances and the occurrence of marked stimulation of acid production upon 

 re-addition of phenol-insulin. Thus phenol seems to act as a stabilizing agent, presumably 

 by preventing destruction of an enzyme, or enzymes, essential for maintenance of a 

 high rate of acid production. In this connection it is of interest that addition of ATP 

 (i mg tetrasodium ATP per ml) to the reaction vessel had no significant effect on (^co 

 either in the presence or absence of extra magnesium, and/or phenol. 



Action of phenol, magnesium, and insulin on melanoma slices 



The responses of melanoma slices to phenol, magnesium, and insulin (Fig. 3) were in 

 marked contrast to those obtained with brain. <2^5 was not stimulated by phenol at any 

 concentration tested (0.02 to 1 .5 mg per ml) . 



400 



350 



"^300 



-.250 



200 



150 



100 



Zn -Insulin 



y^ Phenol +■ 

 Zn -Insulin 



^Control 

 -Phenol 



50 



For example, in eight different experimental 

 runs, involving five separate tumors, addi- 

 tion of 0.4 mg of phenol per ml gave an 

 average lowering of (^co^ oi 15% (range 10 

 to 19 %). However, unlike the results ob- 

 tained with brain slices, the addition of 

 commercial insulin (to give a final concen- 

 tration of 4 units of crystalline zinc-insulin 

 and 0.4 mg phenol per ml) to melanoma 

 preparations gave higher Q^^ values than 

 when equivalent phenol alone was added. 

 When the (2c6 P^^^ commercial insulin was 

 compared with that of the tissue plus 

 phenol alone, it was found in five experi- 

 ments (dextrose 0.625%) that the presence 

 of insulin gave an average stimulation of 

 26% (range 6 to 55%). Because of the 

 inhibiting effect of phenol alone, the effect 

 of commercial insulin (with phenol as 

 preservative) on Qq^ of melanoma slices 

 is more or less masked when comparisons 

 are made with controls to which neither 

 insulin nor phenol have been added. 



In sharp contrast to brain, raising the magnesium level from o.oi mg to 0.4 mg per 

 ml did not increase the (2c6. o^ melanoma slices. Instead the rate was decreased o to 25% 

 (Fig. 3). Again in marked contrast to brain, the acid production by melanoma slices, 

 was increased (Fig. 3) by the various preservative-free preparations of insulin. Crystalline 

 zinc-insulin, rendered free of hyperglycemic factor by tryptic digestion, was as effective 



References p. 346. 



. S-91 Melanoma 

 Anaerobic Glycolysis 



60 70 



Minutes 



Fig. 3. Influence of crystalline zinc-insulin (4 units 

 per ml), phenol (0.4 mg per ml), crystalline zinc- 

 insulin plus phenol, and extra magnesium (0.48 

 mg additional per ml; control = 0.016 mg per 

 ml) on anaerobic acid production in S-91 mela- 

 noma (100 mg wet wt. of slices). 0.625% dex- 

 trose, gas phase 95% Ng and 5% COg- 



