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 DXadministered
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 al1 their differentiated secretory
capacities