Growth-promoting actions of parathyroid hormone, adrenocorticotrophic hormone, and thyroid-stimulating hormone: in vitro studies in normal and pygmy T-lymphoblast cell lines.

We used an in vitro T-lymphoblast clonal proliferation assay to quantify human IGF-I (hIGF-I)-, human PTH (hPTH)-, human ACTH (hACTH)-, and human TSH (hTSH)-stimulated growth of human T-cell leukemia virus-II-transformed T-lymphoblast cell lines from normal individuals and to elucidate the role of IGF-I as the mediator of hPTH-, hACTH-, and hTSH-induced T-cell growth. Normal T-lymphoblast cell lines respond to hIGF-I in a bimodal fashion. The mean first peak response was 143 +/- 9.8% above baseline (defined as 100%) occurring at 8 micrograms/L, and the mean second peak response was 154 +/- 14.4% occurring at 100 micrograms/L. Both responses were completely blocked after incubation with alpha IR-3, an MAb to the IGF-I receptor (by analysis of variance, p = 0.015 between full response curves). After stimulation with hPTH, the mean peak clonal response of normal T-lymphoblast cell lines was 189 +/- 7.0%; after incubation with alpha IR-3, the mean peak clonal response was 108 +/- 7.9% (p = 0.0015 between full response curves). The mean peak clonal response of normal T-lymphoblast cell lines after hACTH stimulation was 192 +/- 8.6%; preincubation with alpha IR-3 reduced the mean peak clonal response to 94 +/- 1.2% (p < 0.0001 between full response curves). With hTSH stimulation, the mean peak clonal response of normal T-lymphoblast cell lines was 167 +/- 7.0%; after incubation with alpha IR-3, the mean peak clonal response was 94 +/- 8.2% (p = 0.003 between full response curves).(ABSTRACT TRUNCATED AT 250 WORDS)