| Autor: |
Filogonio R; Department of Physiological Sciences, Federal University of São Carlos, São Carlos, SP, 13565-905, Brazil. renatofilogonio@gmail.com., Dubansky BD; Department of Biological Sciences, Developmental Integrative Biology Cluster, University of North Texas, Denton, TX, 76203-5220, USA., Dubansky BH; Department of Medical Laboratory Sciences and Public Health, Tarleton State University, Fort Worth, TX, USA., Wang T; Section for Zoophysiology, Department of Biosciences, Aarhus University, 8000, Aarhus C, Denmark., Elsey RM; Louisiana Department of Wildlife and Fisheries, Rockefeller Wildlife Refuge, Grand Chenier, LA, 70643, USA., Leite CAC; Department of Physiological Sciences, Federal University of São Carlos, São Carlos, SP, 13565-905, Brazil., Crossley DA 2nd; Department of Biological Sciences, Developmental Integrative Biology Cluster, University of North Texas, Denton, TX, 76203-5220, USA. |
| Abstrakt: |
Arterial wall tension increases with luminal radius and arterial pressure. Hence, as body mass (M b ) increases, associated increases in radius induces larger tension. Thus, it could be predicted that high tension would increase the potential for rupture of the arterial wall. Studies on mammals have focused on systemic arteries and have shown that arterial wall thickness increases with M b and normalizes tension. Reptiles are good models to study scaling because some species exhibit large body size range associated with growth, thus, allowing for ontogenetic comparisons. We used post hatch American alligators, Alligator mississippiensis, ranging from 0.12 to 6.80 kg (~ 60-fold) to investigate how both the right aortic arch (RAo) and the left pulmonary artery (LPA) change with M b . We tested two possibilities: (i) wall thickness increases with M b and normalizes wall tension, such that stress (stress = tension/thickness) remains unchanged; (ii) collagen content scales with M b and increases arterial strength. We measured heart rate and systolic and mean pressures from both systemic and pulmonary circulations in anesthetized animals. Once stabilized alligators were injected with adrenaline to induce a physiologically relevant increase in pressure. Heart rate decreased and systemic pressures increased with M b ; pulmonary pressures remained unchanged. Both the RAo and LPA were fixed under physiological hydrostatic pressures and displayed larger radius, wall tension and thickness as M b increased, thus, stress was independent from M b ; relative collagen content was unchanged. We conclude that increased wall thickness normalizes tension and reduces the chances of arterial walls rupturing in large alligators. |
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