Incubating plasma membranes prepared from pig liver with varying concentrations of insulin (50—1000 μU/ml) resulted in the release of at least two insulin chemical mediators. One of them was fraction 1 of insulin mediator (M. W. 3700—4000 daltons) which had a significant lipogenesis-stimulatlug activity. The other was fraction 2 of insulin mediator (M. W. about 1000 daltons) which exhibited a lipogenesis-inhibitory activity.The ratio of yield between the two mediators produced from the membranes was not only dependent on the concentration but also on the potency of insulin and its analogs added. The result showed that there was more production of fraction 2 than fraction 1 with the inducer at low concentration (100 μU/ml), while the production of fraction 1 from the plasma membranes incubated with high concentration of insulin (300 μU/ml) was higher than fraction 2. On the other hand, insulin and its analogs which have different biological activities and receptor bindtng activities have been used t
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