Possible Involvement of the Phospholipases in the Mitogenic Actions of Prolactin (PRL) on Nb 2 Node Lymphoma Cells 1

Abstract

The possible role of the phospholipase enzymes in the prolactin stimulation of mitogenesis in Nb₂ node lymphoma cells was investigated. Two phospholipase inhibitors including quinacrine and α-para-dibromoacetophenone (BPB) were employed. Quinacrine at concentrations of 1–5 μM attenuated the magnitude of the PRL stimulation of cell division; at concentrations of 10 μ and above quinacrine abolished the PRL response. BPB at concentrations of 1–10 μM also inhibited the mitogenic effect of PRL in a concentration response fashion. The polyunsaturated fatty acid arachidonic acid partially reversed the inhibitory effects of these drugs. In further studies, exogenously added phospholipase C at concentrations of 5–50 ng/ml was found to potentiate the mitogenic effect of prolactin when prolactin was employed at a concentration that evoked a half-maximal response. By itself, however, phospholipase C had no effect on the rate of cell division. Phospholipase A₂ either by itself or in the presence of prolactin was without effect.