Hypoxia inducible factor (HIF) is a transcription factor that under low environmental
oxygen regulates the expression of suites of genes involved in metabolism, angiogenesis,
erythropoiesis, immune function, and growth. Here, we isolated and sequenced partial
cDNAs encoding hif-α and arnt/hif-β from the Atlantic blue crab, Callinectes sapidus,
an estuarine species that frequently encounters concurrent hypoxia (low O(2)) and
hypercapnia (elevated CO(2)). We then examined the effects of acute exposure (1h)
to hypoxia (H) and hypercapnic hypoxia (HH) on relative transcript abundance for hif-α
and arnt/hif-β in different tissues (glycolytic muscle, oxidative muscle, hepatopancreas,
gill, and gonads) using quantitative real-time RT-PCR. Our results indicate that hif-α
and arnt/hif-β mRNAs were constitutively present under well-aerated normoxia (N) conditions
in all tissues examined. Further, H and HH exposure resulted in both tissue-specific
and muscle fiber type-specific effects on relative hif-α transcript abundance. In
the gill and glycolytic muscle, relative hif-α mRNA levels were significantly lower
under H and HH, compared to N, while no change (or a slight increase) was detected
in oxidative muscle, hepatopancreas and gonadal tissues. H and HH did not affect relative
transcript abundance for arnt/hif-β in any tissue or muscle fiber type. Thus, in crustaceans
the HIF response to H and HH appears to involve changes in hif transcript abundance,
with variation in hif-α and arnt/hif-β transcriptional dynamics occurring in both
a tissue- and muscle fiber type-dependent manner.