A new clonal strain of rat pituitary tumour cells: a model for non-regulated secretion of prolactin

Publisher Website
Google Scholar
Abstract
A new clonal strain of prolactin[Prl]-secreting cells derived from a transplantable rat pituitary tumor, 7315a, has been established in culture. The cells of this strain, designed 235-1, have a highly developed Golgi complex, an extensive rough endoplasmic reticulum, and a few small but no large dense-core granules. When inoculated into athymic mice and rats of the Buffalo strain, the 235-1 cells produce tumors, and the host animals have hypertrophied mammary glands that produce milk, indicating that Prl secreted by these cells has mammotrophic activity. In monolayer culture, the doubling time of 235-1 cells is 31 .+-. 1 h (mean .+-. SE). The cells secrete Prl, a trace quantity of growth hormone [Gh] but no luteinizing hormone [LH], FSH, TSH, ACTH, or .alpha.-MSH. Prl is released at a rate of 257 .+-. 12 fg/h per cell. The cellular content of Prl is 424 .+-. 23 fg/cell. Prl secretion by 235-1 cells is not affected by dopaminergic agonists and antagonists, TRH, or estradiol-17.beta. but is inhibited in the presence of ethylene glycol-.beta.-aminoethyl ether-N,N,N'',N''-tetraacetic acid [EGTA] or monensin, an ionophore that is believed to act at the level of the Golgi complex. The subcellular distribution of Prl in 235-1 cells is different from that in rat pituitary cells. In 235-1 cells, Prl is associated not with a single set of dense particles as it is in pituitary cells but with 2 sets of subcellular particles, of which 1 set cosedimented with particles having lysosomal enzyme activity. Prl secretion by 235-1 cells may involve secretory pathways that are different from those seen in normal lactotrophs.