Destruction of the nuclear morphology of thymic lymphocytes by the corticosteroid cortisol

Abstract

Cortisol (hydrocortisone) at a concentration of 0.27 μ M causes the complete loss of nuclear structure (“pycnosis”) in rat thymocytes maintained in vitro by the initiation during the first hour of exposure of a phosphate-dependent, respiration-linked reaction. The proportion of cells which lose their nuclear structure is directly and linearly proportional to the phosphate concentration in the medium. Under anoxic conditions, cells treated with cortisol cannot develop structureless nuclei. Dinitrophenol can also reduce or prevent the cortisol-induced loss of nuclear structure even at concentrations which do not reduce respiration. These properties of the action of cortisol are identical to those of the actions of ionising radiation, parathyroid hormone and valinomycin. Possible mechanisms underlying the action of cortisol are discussed in the light of available information on the effects of these other agents.