The relationship between growth hormone producing cells in the pars distalis of
the pituitary gland (somatotrophs) and the pineal gland function in rats is nearly not
elucidated, particularly in the aspect of melatonin participation. The current study
tested whether the life-long reduction of endogenous melatonin levels due to pinealcctomy
would.influence the morphological and the ultra structural changes of somatotrophs
as the animals aged, Aging in the pineal-intact animals was associated
with large-sized and shrunken somatotrophs (Type L II and IJI) with dense and irregular
nuclei. The cytoplasm appeared vacuolated. Electron microscopy revealed
somatotrophs with destroyed mitochondrial cristea, The secretory granules were
large, pleomorphic and less electron dense (Type J), scanty (Type II) and overcrowded
with altered electron density (Type IlI). The rough endoplasmic reticulum
(RER) cisternae and Golgi sacules were dilated in all cell types. Aging in the pinealectomized
animals was associated with dilated intercellular spaces and capillaries
engorged with blood. Electron microscopy indicated increased atrophic changes in
both frequency and intensity. No different varieties of cells could be detected. The
nuclei were very dense with irregular outlines. The RER cisternae. the nuclear envelope
and the Golgi sacules were markedly dilated. The findings are consistent with
the idea that the severe cytological changes after pinealectomy were due to reduction
in melatonin since it functions as free radical scavenger and antioxidant. On the other
hand, other pineal secretory products that were reduced as a consequence of pineal
removal may have also been responsible for some of the observed changes, but
this will need further studies.