QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Burton, R. F. Search for Related Content PubMed PubMed Citation Articles by Burton, R. F.

The Journal of Experimental Biology 205, 3587-3600 (2002)
Copyright © 2002 The Company of Biologists Limited

Perspective

Temperature and acid—base balance in ectothermic vertebrates: the imidazole alphastat hypotheses and beyond

Richard F. Burton

Institute of Biomedical and Life Sciences, Thomson Building, University of Glasgow, Glasgow G12 8QQ, UK

e-mail: R.F.Burton{at}bio.gla.ac.uk

Accepted 22 August 2002

Summary

The `imidazole alphastat hypothesis' states that intracellular and extracellular pH, partly via buffering by imidazole groups, change with temperature in a way that keeps imidazole and protein ionization constant, thus maintaining cell function and minimizing shifts of base equivalents and total CO<sub>2</sub>, while adjustment of P<sub>CO2</sub> involves imidazole-based receptors. `The hypothesis', which is actually several hypotheses, has been variously perceived and judged, but its underlying conceptual framework remains largely valid, and is reformulated using differential equations requiring less information input than their integral equivalents. Their usefulness is illustrated with published data on temperature responses in fish cells and whole tetrapods. Mathematical modelling allows general principles to be explored with less immediate concern for uncertainties in experimental data and other information. In tetrapods, it suggests that warming is followed by a loss of base equivalents from the body, and that this loss is due to metabolic adjustments that are not part of pH homeostasis. Uncertainties include intracellular buffer values, local variations in P_CO2 within the body, the possible role of buffering by bone mineral, and the temperature dependence of pK values for CO₂/HCO₃^- and imidazole groups. The equations utilize a single, notional, temperature-dependent pK value for all non-bicarbonate buffers in a given body compartment. This approximates to the `passive component' of pH adjustment to temperature change as measured by the homogenate technique. Also discussed are the diversity of cell responses within individual animals, relevant aspects of the control of ventilation, metabolism and transmembrane transport, and the basis of optimum pH—temperature relationships.

Key words: acid—base balance, alphastat, imidazole alphastat, temperature, pH, carbon dioxide tension, vertebrate, fish, amphibian, reptiles, cell pH

This article has been cited by other articles:

				E. P. Debold, J. Romatowski, and R. H. Fitts The depressive effect of Pi on the force-pCa relationship in skinned single muscle fibers is temperature dependent Am J Physiol Cell Physiol, April 1, 2006; 290(4): C1041 - C1050. [Abstract] [Full Text] [PDF]

				F. Melzner, C. Bock, and H.-O. Portner Critical temperatures in the cephalopod Sepia officinalis investigated using in vivo 31P NMR spectroscopy J. Exp. Biol., March 1, 2006; 209(5): 891 - 906. [Abstract] [Full Text] [PDF]

				Y. Yoshioka, H. Oikawa, S. Ehara, T. Inoue, A. Ogawa, Y. Kanbara, and M. Kubokawa Noninvasive measurement of temperature and fractional dissociation of imidazole in human lower leg muscles using 1H-nuclear magnetic resonance spectroscopy J Appl Physiol, January 1, 2005; 98(1): 282 - 287. [Abstract] [Full Text] [PDF]