ラット培養肝細胞のInsulin-likeGrowth Factor I産生におよぼすInsulin, GlucagonおよびDexamethasoneの影響

We studied the effect of insulin, glucagon or dexamethasone on the production of insulin-like growth factor I (IGF-1) by cultured rat hepatocytes. Hepatocytes were isolated from normal adult rat livers and cultured in MEM, as nearly confluent monolayers. In the absence of such hormones, IGF-I and albumin accumulated in the culture medium almost linearly for periods up to 24 hours with the accumulation rates of 140 mU/mg cell protein per hour and 1.2 μg/mg cell protein per hour, respectively. Cycloheximide (5 μg/ml) almost completely inhibited the accumulation of IGF-1 and albumin in the medium. Insulin at concentrations over 10^-10 M significantly inhibited the production of IGF-1 in spite of the increased production of albumin. Conversely, glucagon stimulated the production of IGF-I at concentrations over 10^-8M,but inhibited the production of albumin at concentrations over 10^-10 M. Dexamethasone stimulated the production of IGF-I at concentrations over 10^-7M,but had no significant effects on the production of albumin. Thus, IGF-1 production of hepatocytes is regulated by several hormones with different manner from albumin production.