AJP - Regulatory, Integrative and Comparative Physiology, Vol 269, Issue 4 814-R821, Copyright © 1995 by American Physiological Society

ARTICLES

Lymphatic regulation of hematocrit during hypoxia in the toad Bufo woodhousei

G. M. Malvin, S. Macias, M. Sanchez, R. Dasalla, A. Park and M. Duran
Cardiopulmonary Physiology Program, Institute for Basic and Applied Medical Research, Lovelace Institutes, Albuquerque, New Mexico 87108, USA.

Hypoxia rapidly increases hematocrit (Hct) in anuran amphibians by reducing plasma volume, but the mechanism(s) mediating this response is unknown. We tested the hypothesis that, during hypoxia, plasma volume is reduced by impaired lymph heart (LH) function, decreasing lymph flow into the circulation. In Bufo woodhousei, we measured the effects of hypoxia on Hct, lymph heart rate (LHR), LH pressure, the movement of dye from the dorsal lymph sac to the arterial blood, and flow through an open LH cannula. We also tested whether splenic contraction or cholinergic nerves contribute to the hypoxia-induced changes. Graded hypoxia between 21 and 4% O2 produced graded increases in Hct (P < 0.0001) and decreases in LHR (P = 0.01). Hypoxia reduced the rate of increase in arterial Evans blue concentration after injection into the dorsal lymph sac (P = 0.041) and decreased flow through an open LH cannula (P < 0.012). Hypoxia increased Hct and reduced LHR similarly in control, splenectomized, and sham-splenectomized toads. Atropine had no significant effect on Hct and LHR. These results indicate that the LHs play a regulatory role in hypoxia-induced hemoconcentration.

This article has been cited by other articles:

				J. B. Andersen, M. S. Hedrick, and T. Wang Cardiovascular responses to hypoxia and anaemia in the toad Bufo marinus J. Exp. Biol., March 1, 2003; 206(5): 857 - 865. [Abstract] [Full Text] [PDF]