The ontogeny of cardio-respiratory function under chronically altered gas compositions in Xenopus laevis.

The importance of diffusion and perfusion in terms of oxygen transport was evaluated by chronically altering environmental O2 availability (hypoxia or hyperoxia) and blood O2 content (carbon monoxide) through development in Xenopus laevis. Oxygen consumption (MO2), individual wet mass, heart rate (fH), and stroke volume (SV) were measured in animals raised from eggs to pre-metamorphic climax while maintained at 11, 21 and 35 kPa O2, combined with and without 2 kPa carbon monoxide. Additionally, cardiac output (Q), and a recently defined O2 consumption/transport quotient (MO2 x QO2(-1)) were calculated. Wet mass, MO2, and fH, were not significantly different between controls and experimental treatments at any developmental stage. However, with hemoglobin oxygen transport blocked by carbon monoxide, the exposed larvae showed an increased SV, Q and MO2 x QO2(-1). Combined, these data suggest that in spite of impaired blood O2 convection, normal aerobic metabolism was maintained, indicating that direct diffusion of O2 plays an important role in supplying oxygen during early development.

[1]  M. Feder.  Effect of developmental stage and body size on oxygen consumption of anuran larvae: A reappraisal , 1982 .

[2]  Peter J. Rombough,et al.  Growth, aerobic metabolism, and dissolved oxygen requirements of embryos and alevins of steelhead, Salmo gairdneri , 1988 .

[3]  Anastasia J. Romanoff,et al.  Biochemistry of the Avian Embryo , 1967 .

[4]  E. Frieden,et al.  Induction and Survival of Hemoglobin-Less and Erythrocyte-Less Tadpoles and Young Bullfrogs , 1968, Science.

[5]  W. Burggren,et al.  Respiration during chronic hypoxia and hyperoxia in larval and adult bullfrogs (Rana catesbeiana). II. Changes in respiratory properties of whole blood. , 1983, The Journal of experimental biology.

[6]  P. Rombough.  Intravascular oxygen tensions in cutaneously respiring rainbow trout (Oncorhynchus mykiss) larvae , 1992 .

[7]  R. Fritsche,et al.  Development of cardiovascular responses to hypoxia in larvae of the frog Xenopus laevis. , 1996, The American journal of physiology.

[8]  D. Ewer,et al.  A Toad (Xenopus lævis) without Hæmoglobin , 1959, Nature.

[9]  P C Hou,et al.  Cardiac output and peripheral resistance during larval development in the anuran amphibian Xenopus laevis. , 1995, The American journal of physiology.

[10]  A. Pinder,et al.  Larval Cardiorespiratory Ontogeny and Allometry in Xenopus laevis , 1995, Physiological Zoology.

[11]  W. Burggren,et al.  Environmental Physiology of the Amphibians , 1993 .

[12]  P. Dejours.  Principles of Comparative Respiratory Physiology , 1975 .

[13]  A. D. Graaf.  A Note on the Oxygen Requirements of Xenopus Laevis , 1957 .

[14]  R. Boutilier,et al.  Blood gases, and extracellular/intracellular acid-base status as a function of temperature in the anuran amphibians Xenopus laevis and Bufo marinus , 1987 .

[15]  M. Feder.  Effect of body size, trophic state, time of day, and experimental stress on oxygen consumption of anuran larvae: An experimental assessment and evaluation of the literature , 1981 .

[16]  J. Gurdon,et al.  Normal table of Xenopus laevis (Daudin) , 1995 .

[17]  J. Faber,et al.  Normal Table of Xenopus Laevis (Daudin) , 1958 .

[18]  C. Rovainen,et al.  Cardiac output in Xenopus laevis tadpoles during development and in response to an adenosine agonist. , 1996, The American journal of physiology.

[19]  P. Territo,et al.  Cardio-respiratory ontogeny during chronic carbon monoxide exposure in the clawed frog Xenopus laevis. , 1998, The Journal of experimental biology.

[20]  S. Warburton,et al.  Patterns of form and function in developing hearts: contributions from non-mammalian vertebrates. , 1994, Cardioscience.

[21]  Hastings,et al.  Developmental changes in oxygen consumption regulation in larvae of the South African clawed frog Xenopus laevis , 1995, The Journal of experimental biology.

[22]  W. Burggren,et al.  Respiration during chronic hypoxia and hyperoxia in larval and adult bullfrogs (Rana catesbeiana). I. Morphological responses of lungs, skin and gills. , 1983, The Journal of experimental biology.

[23]  P. Hou,et al.  Blood pressures and heart rate during larval development in the anuran amphibian Xenopus laevis. , 1995, The American journal of physiology.

[24]  G. F. Holeton.  Respiratory and circulatory responses of rainbow trout larvae to carbon monoxide and to hypoxia. , 1971, The Journal of experimental biology.

[25]  N. Hu,et al.  Hemodynamics of the Stage 12 to Stage 29 Chick Embryo , 1989, Circulation research.