THE ORIGIN, IDENTITY AND FUNCTION OF NEUTRAL‐RED BODIES IN LIVING, FIXED, AND FROZEN‐DRIED ACINOUS CELLS OF THE PANCREAS OF THE MOUSE

SYNOPSIS The effect of injecting mice with 1 ml. each of a saturated solution of neutral‐red chloride in Ringer's solution was studied before making an attempt to determine the origin, identity, and function of neutral‐red bodies in acinous cells of the pancreas. The existence of a neutral‐red “granule” cycle was confirmed. This was partly divided into two main phases: phase I, in which there were a few homogeneously staining granules and phase II, in which there were large numbers of homogeneously staining granules and vacuoles. The neutral‐red granules seen in phase I of the cycle appeared to correspond with granular lipoidal bodies observed either in cells of the same pancreas or in cells of normal (not coloured with neutral red) organs. The neutral‐red granules and vacuoles seen in phase II of the cycle were shown to correspond with granular and vacuolated lipoidal bodies recognized in cells of the same pancreas. In neither phase I nor phase II of the cycle were neutral‐red vacuoles observed amongst zymogen granules. However, vacuolated lipoidal bodies were seen in this position in cells previously coloured with neutral red or in normal cells. All these results are consistent with the view that neutral red first colours preexisting granular lipoidal bodies and is then responsible for the formation of new lipoidal bodies (granular and vacuolated). The neutral‐red bodies were observed to originate in contact with mitochondria. They then passed towards the zymogen zone. In both respects they resemble lipoidal bodies of normal cells. In normal cells lipoidal bodies probably segregate and synthesize substances needed for the formation of zymogen. In cells coloured by neutral red the lipoidal bodies segregate the dye and appear no longer to form zymogen. It would seem that in the latter instance the lipoidal bodies act in a protective capacity and protect the acinous cells from the injurious effects of neutral red. This suggests that under the sustained influence of neutral red, the lipoidal bodies, and therefore the cells, may be deviated from their normal function of synthesizing zymogen. The observations in normal cells that lipoidal bodies originate from mitochondria and then accumulate on the walls of Golgi canals before completing zymogen synthesis, suggests that the Golgi apparatus makes some contribution to lipoidal bodies that enables them finally to complete this synthesis.