A metabolic hypothesis for the evolution of temperature effects on the arterial PCO2 and pH of vertebrate ectotherms

Author:

Hillman Stanley S.1,Hedrick Michael S.2ORCID

Affiliation:

1. Department of Biology, Portland State University, Portland, OR 97207, USA

2. Department of Biological Sciences, California State University East Bay, Hayward, CA 94542, USA

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.

Publisher

The Company of Biologists

Subject

Insect Science,Molecular Biology,Animal Science and Zoology,Aquatic Science,Physiology,Ecology, Evolution, Behavior and Systematics

Cited by 4 articles. 订阅此论文施引文献 订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献

1. A method for measuring meaningful physiological variables in fish blood without surgical cannulation;Scientific Reports;2023-01-17

2. Introduction to the special issue: The state of acid-base physiology in a changing world;Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology;2020-03

3. pH regulation in hibernation: Implications for ventilatory and metabolic control;Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology;2019-11

4. Invited review: Development of acid-base regulation in vertebrates;Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology;2019-10

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