Published In

Journal of Experimental Biology

Document Type

Post-Print

Publication Date

11-17-2017

Subjects

Cold-blooded animals -- Metabolism, Cold-blooded animals -- Hydrogen-ion concentration -- Regulation, Oxygen -- Physiological transport

Abstract

Body temperature increases in ectothermic vertebrates characteristically lead to both increases in arterial PCO2 (PaCO2) and declines in resting arterial pH (pHa) of about 0.017 pH units/°C increase in temperature. This ‘alphastat’ pH pattern has previously been interpreted as being evolutionarily-driven by the maintenance of a constant protonation state on the imidazole moiety of histidine protein residues, hence stabilizing protein structure-function. Analysis of the existing data for interclass responses of ectothermic vertebrates show different degrees of PaCO2 increases and pH declines with temperature between the classes with reptiles>amphibians>fish. The PaCO2 at the temperature where maximal aerobic metabolism (VO2max) is achieved is significantly and positively correlated with temperature for all vertebrate classes. For ectotherms, the PaCO2 where VO2max is greatest is also correlated with VO2max indicating there is an increased driving force for CO2 efflux that is lowest in fish, intermediate in amphibians and highest in reptiles. The pattern of increased PaCO2 and the resultant reduction of pHa to increased body temperature would serve to increase CO2 efflux, O2 delivery, blood buffering capacity and maintain ventilatory scope. This represents a new hypothesis for the selective advantage of arterial pH regulation from a systems physiology perspective in addition to the advantages of maintenance of protein structure-function.

Description

© 2017. Access the most recent version at http://dx.doi.org/10.1242/jeb.168955 Published by The Company of Biologists Ltd.

DOI

10.1242/jeb.168955

Persistent Identifier

http://archives.pdx.edu/ds/psu/22653

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