Effects of pneumadin (PNM) on the adrenal glands. 5. Potent stimulating action of PNM on adrenocortical growth of dexamethasone-administered rats.

Pneumadin (PNM) is a biologically active decapeptide, originally isolated from mammalian lungs, that has been previously found to acutely stimulate pituitary-adrenocortical axis in rats. The effects of 2-day PNM administration on the atrophic adrenal cortices of rats treated for 8 days with dexamethasone (DX) were investigated. PNM significantly raised adrenal weight and the average volume of adrenocortical cells. The decapeptide strikingly increased ACTH plasma concentration; however, the blood levels of aldosterone and corticosterone, as well as steroid output by adrenal quarters were not apparently affected. In light of these findings the following conclusions can be drawn: (i) PNM enhances the growth of adrenal cortex in DX-administered rats by a mechanism involving the stimulation of ACTH release; and (ii) PNM treatment is probably too short to allow DX-atrophied adrenocortical cells to re-acquire all their differentiated secretory capacities.