Chromosomal analysis, organ-specific function and appearance of six clonal strains of rat pituitary tumor cells

Six clonal strains of rat pituitary tumor cells which secrete growth hormone have been serially propagated for periods up to 4 years without loss of organ-specific function. The cells of these strains do not all have the same morphology. We have examined the specific rates of growth hormone production for each cell strain (6.3–95 μg growth hormone/mg cell nitrogen/24 h) and have correlated this differentiated function of each strain with its own karyotype. All strains were aneuploid with modal numbers of chromosomes which were between 69 and 76 per cell. No clear relationships were noted between chromosome number or morphology, appearance of the cells, and the rate of growth hormone production. We conclude that a markedly abnormal karyotype does not by itself preclude organ-specific function in serially propagated strains of neoplastic mammalian cells in culture. Conversely, differentiated function of cells in culture does not necessarily imply the existence of a normal or even near-normal karyotype nor is it correlated with a characteristic appearance of the cells.