Microcirculatory effects of hypoxic and hypercapnic vasoconstriction in frog skin
Malvin, G.
American Journal of Physiology 264(2 Pt 2): R435-R439
1993
ISSN/ISBN: 0002-9513 PMID: 8447501 Document Number: 417134
The effects in frog (albino Xenopus laevis) skin of hypoxic and hypercapnic vasoconstriction on the following microcirculatory parameters were determined: capillary red blood cell flux, capillary red blood cell velocity, perfused capillary density, lineal red blood cell density, and the temporal heterogeneity of capillary red blood cell velocities. All of these parameters affect the gas exchange characteristics of respiratory organs. Measurements were made by fluorescent video microscopy of a 1.5-cm-2 region of skin exposed to different gas mixtures (air, O-2, N-2, 5% CO-2-95% air, 5% CO-2-95% N-2). N-2 caused red blood cell flux and velocity to fall to 52 +- 10% (P lt 0.05) and 47 +- 10% (P lt 0.01), respectively, of those values during air exposure. Five percent CO-2 caused capillary red blood cell flux and velocity to decrease by 51 +- 11% (P lt 0.05) and 43 +- 11% (P lt 0.01), respectively. Fluxes (P lt 0.01) and velocities (P lt 0.01) were also were with 5% CO-2-95% N 2 than with air. There were no significant differences in flux and velocity between N-2, 5% CO-2-95% air and 5% CO-2-95 N-2 (P gt 0.01). There was no significant difference in flux or in velocity between O-2 and air (P gt 0.01). Gas composition had no significant effect on lineal red blood cell density (P gt 0.35) or the density of perfused capillaries (P gt 0.22). The heterogeneity of cell velocities was significantly greater with N-2 than with the other gases (P lt 0.01). There was no significant difference in red blood cell velocity heterogeneity between the other gases (P gt 0.1). These results indicate that besides a reduction in blood flow, hypoxic and hypercapnic vasoconstriction probably has little or no effect on the gas exchange characteristics of the skin.