Pressure-flow relationships in the perfused dog spleen

¹ Biophysics Division, U. S. Army Medical Research Laboratory, Fort Knox, Kentucky, Department of Medicine, Veterans Administration Research Hospital, and Northwestern University Medical School, Chicago, Illinois

Isolated and nonisolated preparations of dog spleens were perfused at various rates by means of a blood pump inserted proximal to the splenic artery. Pressures were measured continuously and vascular resistances were calculated. In both preparations vascular resistance decreased as perfusion pressure gradient increased over a wide range (67–313 mm Hg). Pressures and resistances were consistently lower at each perfusion rate in the isolated preparations, presumably due to periarterial nerve transection. The data suggest that the fall in vascular resistance is primarily brought about by a passive opening of closed channels and a further distention of open vessels unrelated to neurogenic factors. There is no evidence that the smooth muscle of the perfused splenic vascular bed actively contracts as flow and pressure increase.