Changes in the size and number of secretion granules in the rat exocrine pancreas induced by feeding or stimulation in vitro

Abstract

The size, number and volume per cell of secretion granules in rat exocrine pancreas have been measured using stereological techniques. The changes which occur as a result of feeding starved animals (90 min) or stimulating lobular fragments in vitro with carbachol are documented. In fasted animals mean acinar cell volume was estimated as 1670 micron 3 and the cells contained an average of around 450 secretion granules with a corrected mean diameter of 0.70 micron. They occupied around 7% of cell volume. After feeding mean cell volume was about 1300 micron 3 and the cells contained an average of about 190 granules per cell with a mean diameter of 0.58 micron. They occupied 3% of cell volume. A shift in the size frequency distribution of granule diameters occurred as a result of feeding. In vitro experiments in which lobules were induced to secrete with carbachol (10 microM, 3 h, 37 degrees C) had a similar effect. Mean cell volume was reduced from around 1760 micron 3 to 1360 micron 3, mean granule number from around 420 per cell to 180 per cell and the volume density of granules was reduced from about 8% to 3% of cell volume. There was no significant change in mean granule diameter or shift in the size-frequency distribution of granule diameters. Incubation of tissues with cycloheximide (1 mM, 3 h, 37 degrees C) did not prevent secretion by carbachol but it prevented replacement of granules. As a consequence, depletion by carbachol was greater in the presence of cycloheximide, the granules being reduced to around 110 per cell and to only 2.5% of cell volume. We conclude that feeding causes a preferential loss of larger granules and that during secretion replacement of granules occurs. Some of these granules are smaller than those evident in the glands of starved animals.

Rab3D Is Not Required for Exocrine Exocytosis but for Maintenance of Normally Sized Secretory Granules

“…It should be noted that the size of the pancreas zymogen granules is variable and depends on physiological and developmental factors. For instance, in starved animals the diameter of zymogen granules is increased by about 20 to 30% (6,18). We observed a similar increase when comparing starved and fed mice.…”

Morphometry and Elemental Analysis of Rat Exocrine Pancreas following Administration of Trypsin Inhibitor

“…The K increase may reflect heightened protein synthesis [ 15], Acinar cell volume was 1.790 pm3 in the control group and 2,457 pm3 in the experimental group. The control value compares well with the earlier reports of 1,740 urn3 [32], 1,670 pm3 [33] and 1,464-1,804 pm ' for peri-insular cells [34],…”

Selective exocytosis of zymogen granules induces non-parallel secretion in short-term cholecystokinin-stimulated rats

“…Morphological studies had also reported the same effect after feeding (Ermak & Rothman 1981, Aughsteen & Cope 1987) and pharmacological stimulation (Beaudoin et al 1984). Ermak & Rothman (1981) suggested that these changes reflected the loss of protein across the membrane, as proposed in the equilibrium hypothesis (Rothman 1975).…”