Physiological variation of mouse haemoglobins

Abstract

Polymorphism atHbb(haemoglobin β-chain) is widespread in natural populations of the house mouse,Mus musculus, and appears to be maintained by natural selection. This report is an attempt to correlate genotypic fluctuations atHbbwith a most important physiological attribute of haemoglobin, its oxygen carrying capacity. Oxygen affinity has been studied andP50values have been measured in 12 inbred strains as well as wild-caught mice from Skokholm island. The meanP50of each inbred strain is a constant characteristic, although there is high within-strain variation and the oxygen affinity of the blood of an individual can fluctuate considerably from week to week. The causes of this variation remain obscure but neither within-strain nor between-strain differences are correlated with known modulators of oxygen binding. In general, the blood of mice of inbred strains as well as wild-caught mice that are homozygous forHbbdtends to have a higher oxygen affinity than that from comparable animals homozygous forHbb8, but it seems likely that the oxygen dissociation properties of haemoglobin are not the only ones important in determining differential survival of a particularHbbtype under varying environmental stress.