Correlative morphological and biochemical study of the effects of isoprenaline on the organelle and membrane content of the rabbit parotid gland.

A quantitative study has been made on the enzymic, chemical and ultrastructural changes that occur in the parotid glands of rabbits as a result of Isoprenaline-induced secretion. Emphasis has been placed on correlating changes in organelle and membrane content which are evident 2 hr after Isoprenaline administration and which have been measured stereologically with the levels of appropriate enzymic or chemical markers, taking into account the contribution made by both the acinar and duct tissue. Lower protein, alpha-amylase and beta-glycerophosphatase levels correlated with reductions in zymogen granule and lysosome volume with whilst plasmalemmal and Golgi membrane areas and their marker enzyme concentrations remained unchanged. However, declines in alkaline phosphatase and succinate dehydrogenase activity (illustrated histochemically), and p-nitrophenyl phosphatase activity at pH 4-5 in the presence of tartrate occurred without any detectable decrease in membrane area. Conversely, an increase in rough endoplasmic reticulum area was measured stereologically but no increases in chemical markers were detected. The extent of correlation of the data is discussed in the context of the mechanism of secretion and the action of Isoprenaline.