On the involvement of the Golgi apparatus and GERL in processing of secretion products and some enzyme activities in the rat pituitary mammotroph.

Whole pituitary of Wistar albino rats were either (a) immediately fixed in an aldehyde fixative (Karnovsky), or incubated prior to the fixation in (b) unaltered medium 199, (c) medium 199 supplemented with 1.65 M sucrose, or (d) medium 199 diluted with distilled water (1:2). Incubation time was for 0.5 h, at a temperature of 4 degrees or 37 degrees C. All specimens were routinely processed for acid phosphatase (AcPase) or thiamine pyrophosphatase (TPPase) demonstration and examined ultrastructurally. In the control series a and b AcPase activity in the mammotroph was associated with the cisternae of GERL, dense bodies, coated vesicles, immature secretion granules often continuous with cisternae of GERL, and occasionally with the innermost lamellae of the of the Goldi apparatus (GA). TPPase activity was found within the innermost lamellae and the fenestrated element of GA. Occasional granular cores were seen within TPPase-positive lamellae. In all mammotrophs of series (4 degrees and 37 degrees C) severe shrinkage of the lamellae of GA and other membrane-bound structures in the Golgi area was apparent. In some mammotrophs of the series c (37 degrees C) AcPase activity, in addition to its usual sites, was revealed within all lamellae of GA, as well as in some tubular and fenestrated elements continuous with GA. The innermost AcPase-positive lamellae of GA were sometimes partially separated from the others and continuous with immature secretion granules or dense bodies, thus qualifying as cisternae of GERL in the course of their gradual formation from the Golgi lamellae. A gradual increase in AcPase activity from the cis to trans poles of GA could sometimes be noted. TPPase activity in this series spread over ll lamellae of GA and its fenestrated elements. The occasional profiles of rough endoplasmic reticulum and some smooth-surfaced vesicles near GA also gave positive reactions for the enzyme. At 4 degrees C the distributions of both enzyme activities were as in the controls. In all series d (4 or 37 degrees C) the membrane-bounded organelles of the mammotroph were greatly swollen except for occasional cells (at 37 degrees C) in which all lamellae of GA were paradoxically shrunk as in series c. The distributions of AcPase and TPPase activities in series d were as in the controls, except for some cells with shrunken lamellae (at 37 degrees C) in which TPPase activity was spread throughout GA. The results suggest that experimental dehydration of GA in the mammotroph acts by overcoming latency of AcPase and TPPase or by accelerating maturation of AcPase and TPPase activities from their hypothetical precursors thereby tracing the intracellular pathways of these enzymes. It also follows that GA may participate in the initial stage of secretion-granule formation and enzyme activity maturation whereas GERL finalizes the process.