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Alternative splicing of insulin-like growth factor I (IGF-I)/somatomedin C mRNAs generates two IGF-I mRNAs coding for IGF-I peptides with different sequences in the E domain of the IGF-I prohormone. These two mRNAs encode alternative E peptides due to the presence (IGF-Ib) or absence (IGF-Ia) of a 52-base insert in the region coding for the E domain. We have used a solution hybridization/RNase protection assay to determine the tissue distribution and regulation by GH of the expression of these alternative IGF-I mRNAs. IGF-Ib mRNAs are present in low abundance (representing approximately 2.5% of the total IGF-I mRNA) in heart, lung, muscle, testes, stomach, kidney, and brain, but represent approximately 13% of the IGF-I mRNA in liver. GH treatment of hypophysectomized rats increased steady-state IGF-I mRNA levels in liver, kidney, lung, and heart. In kidney, lung, and heart, IGF-Ia and IGF-Ib mRNA levels were coordinately regulated by GH, but, in liver, the fold increase in IGF-Ib mRNA levels was approximately three times greater than the fold increase in IGF-Ia mRNA levels. These data suggest that the processing of IGF-I mRNA in liver is different than in nonhepatic tissues. These results also further elucidate the organization of the rat IGF-I gene as well as the generation of multiple IGF-I mRNAs by alternative splicing.

Two classes of insulin-like growth factor I (IGF-I) cDNAs were isolated from an adult rat liver library using a human IGF-I cDNA probe. The two types of rat IGF-I cDNA differed by the presence or absence of a 52-base pair insert which altered the derived C-terminal amino acid sequence of the E peptide, but not the 3'-untranslated region or the sequence coding for the mature IGF-I protein. When probes derived from these cDNA clones were hybridized to Northern blots of rat mRNA, specific bands of 8.6, 2.1, and 1.0-1.4 kilobases were seen. Hybridization to poly(A)+ RNA from various tissues from GH-treated and control rats demonstrated an increase in IGF-I mRNA due to GH treatment in all tissues examined.

Using monoclonal antibodies to surface antigens, we typed and quantitated the mononuclear cells (MNCs) infiltrating liver tissues from 23 patients with primary sclerosing cholangitis. The circulating T lymphocytes were also enumerated by flow cytometry in 12 of these patients. In blood, T lymphocytes and especially T8+ cells were decreased. T cells were the major components of MNCs (78%) in portal tracts. Few of these cells were Tac+ or HLA-DR+. Total MNCs (929 +/- 90 vs. 106 +/- 18 in controls) included 11% M1+ and 8% B1+ cells. Aggregates of T4+ and T8+ cells were common in portal areas. The portal T4/T8 ratio of 1.27 +/- 0.1 was significantly (p less than 0.01) different than that around proliferating bile ductules (0.8 +/- 0.1). The T8+ and M5+ cells localized in these areas of proliferation and infiltrated ductal epithelium. On the other hand, T4+ cells accumulated on the parenchymal side of fibrosed tissue and densely surrounded certain intralobular bile ducts. Even late in the disease, variability in the extent of MNCs infiltration, ductal proliferation and periductal fibrosis was seen in each biopsy.