Hypoxia and pulmonary arterial pressure in the rabbit

Owen-Thomas, J.B.; Reeves, J. T.

doi:10.1113/jphysiol.1969.sp008779

Cited by 13 publications

(12 citation statements)

References 11 publications

(9 reference statements)

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“…2). Thus, our results suggest that there is an increase in hypoxic reactivity with age, in agreement with those reported in isolated rabbit lungs (14,15).…”

Section: Discussionsupporting

confidence: 82%

“…Rendas et al (10) described an increase in hypoxic reactivity in intact piglets between 2-4 wk and 6 months and correlated this with peripheral extension of arterial smooth muscle to the acinar level. Owen-Thomas and Reeves (14) reported an increase in HPV between 1 and 9-1 1 days in isolated pump-perfused lungs of rabbits. Recently Fike and Hansen (1 5) have extended this finding to show an increase in HPV between 3-8 and 10-14 days in isolated rabbit lungs.…”

Section: Discussionmentioning

confidence: 99%

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Age-Dependent Effects of Indomethacin on Hypoxic Vasoconstriction in Neonatal Lamb Lungs

Tod

et al. 1988

Pediatr Res

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ABSTRACT. Although smooth muscle is abundant in the PVR decreases dramatically when ventilation is initiated at pulmonary vessels of young animals at birth, it is not clear birth (1)(2)(3)(4)(5)(6)(7). This is likely a consequence of mechanical distention if these vessels respond more vigorously to hypoxia than of the lung (1, 2), increased oxygen tension (1, 2), and release of the less muscular vessels of older neonates. To determine dilator PG (2-6). Subsequent decreases in normoxic PVR have the effect of age on the pulmonary vascular response to been well documented in the growing piglet (7) and in other hypoxia during the neonatal period in a single species, we species (2,8,9). In contrast, age-related changes in HPV are less measured the steady-state stimulus-response relationship clear. It has been suggested that the extent of arteriolar muscubetween inspired oxygen tension (200, 50, 30 and 0 mm larization determines the vigor of HPV (10-12). In this case, the Hg) and pulmonary artery pressure-flow curves in isolated newborn animal with its highly muscularized vessels (2, 7, 9, 10) blood perfused lungs from 2-to 4-and 12-to 14-day-old should have a more vigorous hypoxic response than the older lambs. Hypoxic vasoconstriction was attenuated in the animal. Although some studies show an age-dependent decrease younger newborns at an inspired oxygen tension of 50 mm in HPV (8, 13), others report an increase with age (10, 14, 15). Hg, but not at the other oxygen tensions. To determine ifOne possible explanation for these apparently conflicting rethis age-related difference was due to differences in mod-sults is that the vigor of HPV may be influenced by factors other ulation of hypoxic vasoconstriction by cyclooxygenase than vascular muscularization. For instance, there could be ageproducts, we assayed the metabolite of prostacyclin, 6-dependent differences in the modulation of HPV by pulmonary keto-prostaglandin El, in the perfusate and determined the vasodilators. Although vasodilators such as PGI, are released effects of indomethacin (40 pglml) on the hypoxic stimulus-during HPV in both young neonates and mature animals (1 6, response relationship. There was no age-related difference 17), the action and metabolism of various PG may vary with age in perfusate concentration of 6-keto-prostaglandin El, at (18, 19). For example, the vasodilator PGE2 (20) is more slowly any oxygen tension. However, indomethacin reversed the metabolized in the neonate (18). PGD2 is a pulmonary vasodiage-dependent attenuation of hypoxic vasoconstriction at lator in neonatal lambs, but a vasoconstrictor in older animals inspired oxygen tension = 50 mm Hg such that in indo-(21-23). Such differences may be partially responsible for the methacin-treated lungs pulmonary vasomotor tone was variable effects of cyclooxygenase inhibition on the developing higher in 2-to 4-day-old lungs than in 12-to 14-day-old pulmonary vasculature. In the intact pig, meclofenamate inlungs. This marked enhancement of hypoxic reactivity by creased normoxic PV...

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“…2). Thus, our results suggest that there is an increase in hypoxic reactivity with age, in agreement with those reported in isolated rabbit lungs (14,15).…”

Section: Discussionsupporting

confidence: 82%

Section: Discussionmentioning

confidence: 99%

Age-Dependent Effects of Indomethacin on Hypoxic Vasoconstriction in Neonatal Lamb Lungs

Tod

et al. 1988

Pediatr Res

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“…Other investigators have demonstrated similar magnitudes of increase in pulmonary arterial pressor in response to hypoxia in isolated lungs of newborn lambs (12) and adult rabbits (9), as compared to intact preparations using the same species (4,9). Thus, we believe our findings in isolated newborn rabbit lungs might represent findings in the living animal.…”

Section: Respiratorymentioning

confidence: 50%

“…We previously showed that the hypoxic pressor response was greater in lungs of 10-to 14-d-old than 3-to 8-d-old rabbits (1 1). Other investigators have also found that the magnitude of the pulmonary arterial pressor response to hypoxia varies with postnatal age (9,16). Differences in postnatal ages between groups of animals in this study, therefore, most likely explain differences in hypoxic pressor responses between them.…”

Section: Respiratorymentioning

confidence: 53%

The Effect of Alkalosis on Hypoxia-Induced Pulmonary Vasoconstriction in Lungs of Newborn Rabbits

Fike

Hansen

1989

Pediatr Res

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ABSTRACT. The purpose of this study was to determine alkalosis reduces hypoxia-induced pulmonary vasoconstriction whether metabolic and respiratory alkalosis reduce hy-in lungs of a newborn animal. We also wanted to determine if poxia-induced pulmonary vasoconstriction in lungs of new-metabolic and respiratory-induced alkalosis have similar effects born rabbits. To accomplish this, we isolated and perfused on hypoxic pulmonary vaosconstriction. Finally, we wondered with blood the lungs from 33 newborn rabbits, 3-14 d old. if inducing alkalosis during versus before exposure to hypoxia In all pairs of lungs, we first measured the magnitude of would produce different results. To accomplish these goals, we hypoxia-induced pulmonary vasoconstriction a t a p H of first measured the magnitude of hypoxia-induced pulmonary 7.30-7.42. We then measured the effect of alkalosis on the vasoconstriction at a pH of 7.30-7.42 in isolated, perfused lungs magnitude of hypoxic pulmonary vasoconstruction by fol-of newborn rabbits. Next, in some lungs we repeated the hypoxic lowing one of two different sequences of exposure to hy-challenge and during hypoxia induced respiratory or metabolic poxia and alkalosis. For the first sequence, we exposed 13 alkalosis. In other lungs, we induced respiratory or metabolic lungs to hypoxia, and during the hypoxic exposure we alkalosis and then repeated the hypoxic challenge. We found that either decreased the inspired Pcoz (respiratory alkalosis, n both metabolic and respiratory alkalosis decreased the magnitude = 8) or infused N a H C 0 3 (metabolic alkalosis, n = 5) to of hypoxia-induced pulmonary vasoconstriction when alkalosis achieve a p H of 7.50-7.65. For the second sequence, we was induced during the hypoxic challenge. In contrast, when first decreased the inspired Pco2 (n = 9) or infused Na-either mode of alkalosis was induced before hypoxia, pulmonary H C 0 3 (n = 11) to achieve a p H of 7.50-7.65 and then arterial vasoconstriction was not decreased. We conclude that exposed the lungs to hypoxia. We found that hypoxic respiratory and metabolic alkalosis have similar effects on hypulmonary vasoconstriction was reduced by either respi-poxia-induced pulmonary vasoconstriction in lungs of newborn ratory or metabolic alkalosis, when alkalosis was induced rabbits. Both types of alkalosis reduce ongoing hypoxic pulmoduring hypoxia. When respiratory or metabolic alkalosis nary vasoconstriction, and neither diminishes vasoconstriction was induced before hypoxia, the magnitude of hypoxia-in response to subsequent hypoxia. induced pulmonary vasoconstriction was the same as at the normal pH. We conclude that both metabolic and respira-MATERIALS AND METHODS tory alkalosis reduce ongoing hypoxic pulmonary vasoconstriction in lungs of newborn rabbits. However, neither Surgicu/prepurution. We anesthetized 33 New Zealand White mode of alkalosis blunts pulmonary vasoconstriction in newborn rabbit Pups, ages 3-14 d, wt 148 + 52 g, with sodium response to subsequent exposures to hypoxia. (Pediatr Res pento...

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“…Features such as vascular reactivity, pulmonary capillary recruitment, and metabolic capabilities of the microvasculature appear to differ between adult and immature animals (1)(2)(3)(4)(5)(6)(7)(8). Recently, the fractal spatial distribution and isogravitational heterogeneity of pulmonary blood flow (PBF) have been delineated in adult animals using injectable microspheres that achieved greater resolution than earlier studies (9,10).…”

mentioning

confidence: 99%

Spatial and Temporal Heterogeneity of Regional Pulmonary Blood Flow in Piglets

et al. 2007

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ABSTRACT:Regional pulmonary blood flow (PBF) in adult animals varies over space and time, following a fractal pattern. We hypothesized that PBF would follow a fractal pattern in young animals. Five, two-week old piglets were sedated and mechanically ventilated. After stabilization, fluorescent microspheres were injected via the right atrium at baseline and then again at 5, 20, 20.5, 40 and 60 min. The lungs were subsequently excised, dried, inflated, and cored into 0.12-cm 3 pieces (mean n ϭ 561 Ϯ 106 per animal) with the spatial coordinates recorded for each piece. Regional PBF was spatially and temporally heterogeneous with a spatial coefficient of variation of 43.3 Ϯ 7.9% and a temporal coefficient of variation of 14.3 Ϯ 0.4%. PBF followed a fractal pattern with a fractal dimension of 1.20 Ϯ 0.06 at 20 min, remaining stable throughout the experiment. PBF decreased with distance from the hilum but did not follow a lobar pattern. Temporal heterogeneity did not significantly increase with time but low flow regions demonstrated the greatest temporal variability throughout the study. Hence, PBF in young piglets was characterized both spatial and temporal heterogeneity. A considerable amount of information describing the structural and functional characteristics of the pulmonary circulation during postnatal lung development exists. Features such as vascular reactivity, pulmonary capillary recruitment, and metabolic capabilities of the microvasculature appear to differ between adult and immature animals (1-8). Recently, the fractal spatial distribution and isogravitational heterogeneity of pulmonary blood flow (PBF) have been delineated in adult animals using injectable microspheres that achieved greater resolution than earlier studies (9,10). The results of these studies diverge from the findings of homogeneous gravitational zones described by West et al. (11). Temporal heterogeneity also occurs in the pulmonary circulation, which may subserve the conservation of energetics rather than ventilation-perfusion relationships (12).Hitherto, these physiologic characteristics remain unstudied in newborn or very young animals. Speculation suggests that the fractal nature of PBF is based on the pulmonary anatomy, particularly of the precapillary bed (13). If true, the spatial distribution of PBF in young animals should be similar to that in adults. Furthermore, the presence of temporal heterogeneity of PBF in young animals has not been reported. Previous studies suggest a higher degree of pulmonary vascular reactivity in neonatal animals (2,3,6) compared with adults, and hence temporal heterogeneity should be greater than that previously described in adult animals.We measured spatial and temporal heterogeneity in piglets because morphometric studies of pulmonary development in the piglet suggest that the vascular and alveolar changes during the first 3 months of life are similar to those seen in humans (14,15). We hypothesized that under normoxic conditions the pulmonary blood flow would demonstrate greater spatial heteroge...

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Hypoxia and pulmonary arterial pressure in the rabbit

Cited by 13 publications

References 11 publications

Age-Dependent Effects of Indomethacin on Hypoxic Vasoconstriction in Neonatal Lamb Lungs

Age-Dependent Effects of Indomethacin on Hypoxic Vasoconstriction in Neonatal Lamb Lungs

The Effect of Alkalosis on Hypoxia-Induced Pulmonary Vasoconstriction in Lungs of Newborn Rabbits

Spatial and Temporal Heterogeneity of Regional Pulmonary Blood Flow in Piglets

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