ANOXIC AND SECRETORY VACUOLATION IN THE ACINAR CELLS OF THE PANCREAS

¹ Physiological Laboratory, Downing Place, Cambridge

Vacuoles, 2-20µ in diameter, develop in the acinar cells of the rat pancreas when small cubes (2mm³) of tissue are incubated for 1 hr at 20° C in unoxygenated media such as Tyrode's solution or rat's serum. For vacuolation to occur the cells must be anoxic and have access to excess fluid containing Ca²⁺ and either Na⁺ or Li⁺. The vacuoles are bounded by a membrane and develop from or near the Golgi complex. Vacuolation is prevented if the medium is cooled to 0° C, if 270 m-osmoles of sucrose, glucose or glycerol is added to the medium, or if the essential cations are not available: it is not prevented by the addition of 270 m-osmoles of urea or propylene glycol, by the addition of poisons which block oxidative phosphorylation or glycolysis, or by substituting Li⁺ for Na⁺. Vacuolation can be increased by allowing the tissue to stand at 20° C for 15 or 30 min before immersion in a suitable medium. It is suggested that vacuolation involves two distinct, passive movements of fluid, firstly from the external medium into the cytoplasmic matrix, and then from the matrix into the vacuoles. The second movement appears to involve the enzymic breakdown of large, precursor molecules in some part of the Golgi complex. Vacuolation was also induced by massive stimulation in vivo using a mixture of acetyl choline and eserine. It is suggested that anoxic vacuolation and secretory vacuolation share a common mechanism.

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