Identification of insulin-like growth factor binding proteins from cultured XXXX epidermal keratinocytes.

@entity1 @entity19518 @entity12561 @entity2301 @entity10513 @entity442 @entity10116 @entity71335 @entity54738 @entity71334 @entity11428 @entity291
The role and mechanisms of action of insulin-like growth factors (IGFs) in skin remain unclear. Epidermal keratinocytes possess @entity442 receptors and are responsive to @entity442 , which is primarily derived from underlying dermal fibroblasts. IGF binding proteins (IGFBPs), also synthesized by fibroblasts, may be involved in paracrine targeting of @entity442 to its receptors. We therefore examined whether @entity1 keratinocytes synthesize IGFBPs and their mRNAs. Following culture in complete medium (containing @entity291 pituitary extract and @entity11428 ) Western ligand blotting (WLB) of cell conditioned medium revealed a major band of 32 kD, a less abundant IGFBP of 24 kD at all passages, and a 37-42 kD IGFBP which increased in abundance in late passage. Immunoprecipitation followed by WLB confirmed that the predominant 32 kD band was @entity10513 . Radioimmunoassay of @entity71334 revealed detectable levels of @entity2301 and significant levels of @entity19518 , but not @entity10116 . Northern analysis following culture in complete medium revealed that at early passage @entity71335 mRNAs were detectable. @entity54738 mRNAs were not detectable. Following culture in growth factor-free medium a 37-42 kD band, consistent with @entity2301 , was predominant and a 24 kD band consistent with @entity12561 was also present. These data demonstrate the expression of a distinct pattern of IGFBPs by cultured @entity1 keratinocytes dependent on culture conditions. Keratinocyte-derived IGFBPs are likely to play a role in the transport and targeting of @entity442 from dermally derived fibroblasts to the epidermis.
