Analysis of steroid resistance in lymphoid cell hybrids.

In an attempt to obtain a more detailed understanding of the action of the glucocorticoid-receptor complex in mouse lymphoid cell lines, steroid sensitivity has been investigated in hybrids. Hybrids between dexamethasone (dex)-sensitive and dexamethasone-resistant (Dexr) variants, and hybrids between different Dexr variants were investigated. In the case of Dexr x Dexs hybrids, the possibility of negative complementation was tested; in the case of Dexr x Dexr hybrids, positive complementation was investigated. Neither positive nor negative complementation could be detected; dex sensitivity was always dominant over dex resistance. However, hybrids which contain positive receptor allele(s) segregated out Dexr clones at higher frequencies than expected from studies of pseudodiploid cell lines. This study suggests that different mechanisms give rise to the dex-resistant phenotype in pseudodiploid lymphoid cell lines and in pseudotetraploid hybrids of these cell lines.