Influence of granulocyte-macrophage colony stimulating factor on pituitary-adrenal axis (PAA) in rats in vivo.

We have studied the in vivo influence of granulocyte-macrophage colony stimulating factor (GM-CSF) on blood plasma concentration of adrenocorticotropic hormone (ACTH) and corticosterone in Wistar rats. The administration of 10 micrograms/kg b.w. GM-CSF at 45 (P < 0.01), 90 (P < 0.01) and at 45 (P < 0.001), 90 (P < 0.001) and 180 min (P < 0.001) increased the secretion of ACTH and corticosterone, respectively. Prolonged administration of 10 micrograms/kg b.w. of GM-CSF increased the ACTH (P < 0.001) and corticosterone (P < 0.001) concentration in blood plasma. We have also found that chronic treatment with 10 micrograms/kg b.w. of GM-CSF increased the proliferative activity of corticotrophs (P < 0.05), but it did not significantly change the total cell proliferation in the anterior pituitary gland. Moreover, this cytokine increased cell proliferation of the adrenal cortex (P < 0.001). These experiments suggest that GM-CSF activates the pituitary-adrenal axis and support the hypothesis of bidirectional associations between the immune and neuroendocrine systems.