Permeability of gastric capillaries to small and large molecules.
The permeability of capillaries in the stomach to small and large solutes was studied with the double-indicator diffusion technique in the dog stomach and by analysis of steady-state lymph and plasma samples in the cat stomach. The effective pore radius in gastric capillaries determined by indicator diffusion was 53 A, whereas steady-state lymph samples predicted a small-pore radius of 47 A. At the highest plasma flow rates studied (achieved by intra-arterial infusion of isoproterenol), indicator diffusion estimates of the permeability-surface area product for raffinose, inulin, and beta-lactoglobulin A were 140, 70, and 8 ml . min-1 . 100 g-1, respectively. The lymph studies indicate that gastric capillaries are more permeable than capillaries in the intestine and colon to albumin and larger molecules. The calculated effective large-pore radius of gastric capillaries was 250 A. The osmotic reflection coefficients (sigma d) ranged from 0.73 +/- 0.03 for albumin to 0.91 +/- 0.02 for beta-lipoprotein (120-A radius). The sigma d for total plasma protein was 0.78 +/- 0.03, indicating a substantial transcapillary oncotic pressure gradient, despite the greater permeability of these capillaries for macromolecules.
D000818:Animals; D001798:Blood Proteins / Q000378:metabolism*; D002199:Capillary Permeability; D002415:Cats; D004285:Dogs; D007444:Inulin; D007782:Lactoglobulins; D008196:Lymph / Q000502:physiology; D008970:Molecular Weight; D009994:Osmolar Concentration; D011887:Raffinose; D012039:Regional Blood Flow; D012212:Rheology; D013270:Stomach / Q000098:blood supply*; D005719:gamma-Globulins
D001798:Blood Proteins; D007782:Lactoglobulins; D005719:gamma-Globulins; D007444:Inulin; D011887:Raffinose