Fine structure of the pars distalis and interrenals of Taricha torosa after administration of metopirone (SU-4885)

Three tinctorially different cell types have been observed in the pars distalis of the newt, Taricha torosa, by light microscopy, whereas five granulated cell types and one nongranulated stellate cell have been revealed in this gland by electron microscopy. The adrenalectomy cells of this species, observed after treatment with the adrenocortical inhibitor. Metopirone, contain secretory granules with maximum diameters of 200 mμ and appear to be derived from the type II cells. The release of secretory granules from the adrenalectomy cells is by exocytosis, a mechanism observed frequently in the pars distalis of higher vertebrates but not previously described in the amphibian pituitary.Fine structural alterations of the mitochondria and lipid droplets of the interrenal cells after Metopirone treatment are also discussed.