Insulin-mediated inhibition of tyrosinase activity and protein synthesis in melanoma cell cultures

Insulin lowers basal levels of tyrosinase activity and inhibits the MSH-stimulated rise in tyrosinase in Cloudman S-91 mouse melanoma cell cultures. These cultures are very sensitive to insulin. A concentration of insulin as low as 5 x 10 M insulin produces optimum inhibition. At maximum inhibition, tyrosinase activity is reduced to approximately 50% of control levels. Insulin inhibits cellular proliferation in melanoma cells; however, inhibition of tyrosinase activity precedes this effect. Insulin also inhibits the (Bu)2 cAMP and theophylline stimulated rise in enzyme activity. This finding suggests that insulin exerts its effects at a site distal to cAMP production. Insulin, in fact, does not lower cAMP levels in melanoma cells, nor does it alter the MSH-stimulated rise of cAMP. The inhibitory effect of insulin on tyrosinase activity could not be mimicked by either (Bu)2 cGMP or 8-bromo-cGMP, suggesting that insulin does not exert its effects by altering cellular levels of this nucleotide. Insulin decreases the incorporation of [3H]-leucine into trichloracetic acid insoluble material by 50%, an inhibition which corresponds well with the observed level of reduction of tyrosinase activity. This finding suggests that the inhibition of tyrosinase activity may be caused by a general reduction in protein synthesis due to insulin treatment.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Masters

Grantor dc:publisher

Texas Tech University

Year dc:date.issued

1984

Author dc:creator

• Ehlers, Susan Elizabeth

• Proteins -- Synthesis
• Melanoma
• Insulin
• Phenol oxidase
• Enzyme inhibitors
• Rats -- Physiology

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/2346/14235

OAI identifier oai:identifier

oai:ttu-ir.tdl.org:2346/14235