Studies on secretory activity in the pars intermedia of Xenopus laevis 2: A biochemical and electron cytochemical investigation of acid hydrolase activity following the stimulation of secretory activity in vivo

In the MSH cell at the onset of secretory activity, acid hydrolase activity increases. This increased activity, shown quantitatively by assaying beta-glycerophosphatase and R-glucuronidase within the stimulated gland, has been shown by electron cytochemical methods for beta-glycerophosphatase (acid phosphatase) and aryl sulphatase to be related to the production of large numbers of dense bodies. Cytochemical evidence also supports the view that these lytic bodies arise from GERL-like cisternal elements since it is shown that in addition to the flattened, parallel Golgi cisternae these elements are also R-glycerophosphatase-positive. The similarities between the dense bodies and those of other cell types are described and discussed.