Isolation of rat somatotroph and mammotroph secretory granules by equilibrium density centrifugation in a linear metrizamide gradient.

A procedure has been developed for separating rat somatotroph and mammotroph secretory granules from other membranous organelles. The approach devised is a 6-step procedure involving filtration and equilibrium and rate density-gradient centrifugation in Metrizamide gradients of low ionic strength. The use of Metrizamide minimizes disruption and solubilization of the contents of these granules. The majority of the somatotroph and mammotroph granules can be isolated in a gradient fraction virtually free of any mitochondria, microsomes or other secretory granules.