科研之友
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摘要
The nests of embryonic turtles naturally experience elevated CO2 (hypercarbia), which leads to increased blood P-CO2 and a respiratory acidosis, resulting in reduced blood pH [extracellular pH (pH(e))]. Some fishes preferentially regulate tissue pH [intracellular pH (pH(i))] against changes in pHe; this has been proposed to be associated with exceptional CO2 tolerance and has never been identified in amniotes. As embryonic turtles may be CO2 tolerant based on nesting strategy, we hypothesized that they preferentially regulate pH(i), conferring tolerance to severe acute acid-base challenges. This hypothesis was tested by investigating pH regulation in common snapping turtles (Chelydra serpentina) reared in normoxia then exposed to hypercarbia (13 kPa PCO2) for 1 h at three developmental ages: 70% and 90% of incubation, and yearlings. Hypercarbia reduced pH(e) but not pH(i), at all developmental ages. At 70% of incubation, pH(e) was depressed by 0.324 pH units while pH(i) of brain, white muscle and lung increased; heart, liver and kidney pHi remained unchanged. At 90% of incubation, pH(e) was depressed by 0.352 pH units but heart pH(i) increased with no change in pH(i) of other tissues. Yearlings exhibited a pHe reduction of 0.235 pH units but had no changes in pH(i) of any tissues. The results indicate common snapping turtles preferentially regulate pH(i) during development, but the degree of response is reduced throughout development. This is the first time preferential pH(i) regulation has been identified in an amniote. These findings may provide insight into the evolution of acid-base homeostasis during development of amniotes, and vertebrates in general.
- 出版日期2016-7
