1kb /3-actin cDNA (11) was released by BamHl digestion; the 662-base pair full length IGF-1 cDNA was obtained from plasmid phIGF-1 (12) by Pstl digestion; the Xbal-BamH\ fragment of the human IGF1-R cDNA was released from plasmid pCVN-IGF-lR