Immunoreactive gastrin in differential and density gradient fractions of rat gastric mucosa

Immunoreactive gastrin was measured in subcellular fractions of rat gastric mucosa. The sedimentational properties of subcellular gastrin-containing structures were distinct from those of mitochondria. After centrifugation in sucrose density gradients using a zonal rotor, the peak of immunoreactive gastrin was found in 1-17--1-18 g cm(-3) density sucrose (1-35 M; 39-5%, W/W). A thermolabile component with 125I-labelled gastrin-binding activity present in gastric mucosal homogenates and fractions was not associated with the gastrin storage vesicles sedimenting in density gradients.