Protection against high intravascular pressure in giraffe legs

Karin Kastberg Petersen; Arne Hørlyck; Kristine Hovkjær Østergaard; Jørgen Andresen; Torbjørn Halle Brøgger; Nini Skovgaard Jensen; Niklas Telinius; Ismael Laher; Mads Frost Bertelsen; Carsten Grøndahl; Morten Holdgaard Smerup; Niels H. Secher; Emil Toft Brøndum; John M. Hasenkam; Tobias Wang; Ulrik Baandrup; Christian Aalkjær

doi:10.1152/ajpregu.00025.2013

Protection against high intravascular pressure in giraffe legs

Karin Kastberg Petersen, Arne Hørlyck, Kristine Hovkjær Østergaard, Jørgen Andresen, Torbjørn Halle Brøgger, Nini Skovgaard Jensen, Niklas Telinius, Ismael Laher, Mads Frost Bertelsen, Carsten Grøndahl, Morten Holdgaard Smerup, Niels H. Secher, Emil Toft Brøndum, John M. Hasenkam, Tobias Wang, Ulrik Baandrup, Christian Aalkjær

Department of Clinical Medicine

15 Citations (Scopus)

Abstract

The high blood pressure in giraffe leg arteries renders giraffes vulnerable to edema. We investigated in 11 giraffes whether large and small arteries in the legs and the tight fascia protect leg capillaries. Ultrasound imaging of foreleg arteries in anesthetized giraffes and ex vivo examination revealed abrupt thickening of the arterial wall and a reduction of its internal diameter just below the elbow. At and distal to this narrowing, the artery constricted spontaneously and in response to norepinephrine and intravascular pressure recordings revealed a dynamic, viscous pressure drop along the artery. Histology of the isolated median artery confirmed dense sympathetic innervation at the narrowing. Structure and contractility of small arteries from muscular beds in the leg and neck were compared. The arteries from the legs demonstrated an increased media thickness-to-lumen diameter ratio, increased media volume, and increased numbers of smooth muscle cells per segment length and furthermore, they contracted more strongly than arteries from the neck (500 ± 49 vs. 318 ± 43 mmHg; n = 6 legs and neck, respectively). Finally, the transient increase in interstitial fluid pressure following injection of saline was 5.5 ± 1.7 times larger (n = 8) in the leg than in the neck. We conclude that 1) tissue compliance in the legs is low; 2) large arteries of the legs function as resistance arteries; and 3) structural adaptation of small muscle arteries allows them to develop an extraordinary tension. All three findings can contribute to protection of the capillaries in giraffe legs from a high arterial pressure.

Original language	English
Journal	American Journal of Physiology: Regulatory, Integrative and Comparative Physiology
Volume	305
Issue number	9
Pages (from-to)	R1021-R1030
Number of pages	10
ISSN	0363-6119
DOIs	https://doi.org/10.1152/ajpregu.00025.2013
Publication status	Published - 1 Nov 2013

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Petersen, K. K., Hørlyck, A., Østergaard, K. H., Andresen, J., Brøgger, T. H., Jensen, N. S., Telinius, N., Laher, I., Bertelsen, M. F., Grøndahl, C., Smerup, M. H., Secher, N. H., Brøndum, E. T., Hasenkam, J. M., Wang, T., Baandrup, U., & Aalkjær, C. (2013). Protection against high intravascular pressure in giraffe legs. American Journal of Physiology: Regulatory, Integrative and Comparative Physiology, 305(9), R1021-R1030. https://doi.org/10.1152/ajpregu.00025.2013

Petersen, KK, Hørlyck, A, Østergaard, KH, Andresen, J, Brøgger, TH, Jensen, NS, Telinius, N, Laher, I, Bertelsen, MF, Grøndahl, C, Smerup, MH, Secher, NH, Brøndum, ET, Hasenkam, JM, Wang, T, Baandrup, U & Aalkjær, C 2013, 'Protection against high intravascular pressure in giraffe legs', American Journal of Physiology: Regulatory, Integrative and Comparative Physiology, vol. 305, no. 9, pp. R1021-R1030. https://doi.org/10.1152/ajpregu.00025.2013

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title = "Protection against high intravascular pressure in giraffe legs",

abstract = "The high blood pressure in giraffe leg arteries renders giraffes vulnerable to edema. We investigated in 11 giraffes whether large and small arteries in the legs and the tight fascia protect leg capillaries. Ultrasound imaging of foreleg arteries in anesthetized giraffes and ex vivo examination revealed abrupt thickening of the arterial wall and a reduction of its internal diameter just below the elbow. At and distal to this narrowing, the artery constricted spontaneously and in response to norepinephrine and intravascular pressure recordings revealed a dynamic, viscous pressure drop along the artery. Histology of the isolated median artery confirmed dense sympathetic innervation at the narrowing. Structure and contractility of small arteries from muscular beds in the leg and neck were compared. The arteries from the legs demonstrated an increased media thickness-to-lumen diameter ratio, increased media volume, and increased numbers of smooth muscle cells per segment length and furthermore, they contracted more strongly than arteries from the neck (500 ± 49 vs. 318 ± 43 mmHg; n = 6 legs and neck, respectively). Finally, the transient increase in interstitial fluid pressure following injection of saline was 5.5 ± 1.7 times larger (n = 8) in the leg than in the neck. We conclude that 1) tissue compliance in the legs is low; 2) large arteries of the legs function as resistance arteries; and 3) structural adaptation of small muscle arteries allows them to develop an extraordinary tension. All three findings can contribute to protection of the capillaries in giraffe legs from a high arterial pressure.",

author = "Petersen, {Karin Kastberg} and Arne H{\o}rlyck and {\O}stergaard, {Kristine Hovkj{\ae}r} and J{\o}rgen Andresen and Br{\o}gger, {Torbj{\o}rn Halle} and Jensen, {Nini Skovgaard} and Niklas Telinius and Ismael Laher and Bertelsen, {Mads Frost} and Carsten Gr{\o}ndahl and Smerup, {Morten Holdgaard} and Secher, {Niels H.} and Br{\o}ndum, {Emil Toft} and Hasenkam, {John M.} and Tobias Wang and Ulrik Baandrup and Christian Aalkj{\ae}r",

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doi = "10.1152/ajpregu.00025.2013",

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T1 - Protection against high intravascular pressure in giraffe legs

AU - Petersen, Karin Kastberg

AU - Hørlyck, Arne

AU - Østergaard, Kristine Hovkjær

AU - Andresen, Jørgen

AU - Brøgger, Torbjørn Halle

AU - Jensen, Nini Skovgaard

AU - Telinius, Niklas

AU - Laher, Ismael

AU - Bertelsen, Mads Frost

AU - Grøndahl, Carsten

AU - Smerup, Morten Holdgaard

AU - Secher, Niels H.

AU - Brøndum, Emil Toft

AU - Hasenkam, John M.

AU - Wang, Tobias

AU - Baandrup, Ulrik

AU - Aalkjær, Christian

PY - 2013/11/1

Y1 - 2013/11/1

N2 - The high blood pressure in giraffe leg arteries renders giraffes vulnerable to edema. We investigated in 11 giraffes whether large and small arteries in the legs and the tight fascia protect leg capillaries. Ultrasound imaging of foreleg arteries in anesthetized giraffes and ex vivo examination revealed abrupt thickening of the arterial wall and a reduction of its internal diameter just below the elbow. At and distal to this narrowing, the artery constricted spontaneously and in response to norepinephrine and intravascular pressure recordings revealed a dynamic, viscous pressure drop along the artery. Histology of the isolated median artery confirmed dense sympathetic innervation at the narrowing. Structure and contractility of small arteries from muscular beds in the leg and neck were compared. The arteries from the legs demonstrated an increased media thickness-to-lumen diameter ratio, increased media volume, and increased numbers of smooth muscle cells per segment length and furthermore, they contracted more strongly than arteries from the neck (500 ± 49 vs. 318 ± 43 mmHg; n = 6 legs and neck, respectively). Finally, the transient increase in interstitial fluid pressure following injection of saline was 5.5 ± 1.7 times larger (n = 8) in the leg than in the neck. We conclude that 1) tissue compliance in the legs is low; 2) large arteries of the legs function as resistance arteries; and 3) structural adaptation of small muscle arteries allows them to develop an extraordinary tension. All three findings can contribute to protection of the capillaries in giraffe legs from a high arterial pressure.

AB - The high blood pressure in giraffe leg arteries renders giraffes vulnerable to edema. We investigated in 11 giraffes whether large and small arteries in the legs and the tight fascia protect leg capillaries. Ultrasound imaging of foreleg arteries in anesthetized giraffes and ex vivo examination revealed abrupt thickening of the arterial wall and a reduction of its internal diameter just below the elbow. At and distal to this narrowing, the artery constricted spontaneously and in response to norepinephrine and intravascular pressure recordings revealed a dynamic, viscous pressure drop along the artery. Histology of the isolated median artery confirmed dense sympathetic innervation at the narrowing. Structure and contractility of small arteries from muscular beds in the leg and neck were compared. The arteries from the legs demonstrated an increased media thickness-to-lumen diameter ratio, increased media volume, and increased numbers of smooth muscle cells per segment length and furthermore, they contracted more strongly than arteries from the neck (500 ± 49 vs. 318 ± 43 mmHg; n = 6 legs and neck, respectively). Finally, the transient increase in interstitial fluid pressure following injection of saline was 5.5 ± 1.7 times larger (n = 8) in the leg than in the neck. We conclude that 1) tissue compliance in the legs is low; 2) large arteries of the legs function as resistance arteries; and 3) structural adaptation of small muscle arteries allows them to develop an extraordinary tension. All three findings can contribute to protection of the capillaries in giraffe legs from a high arterial pressure.

U2 - 10.1152/ajpregu.00025.2013

DO - 10.1152/ajpregu.00025.2013

M3 - Journal article

SN - 0363-6119

VL - 305

SP - R1021-R1030

JO - American Journal of Physiology: Regulatory, Integrative and Comparative Physiology

JF - American Journal of Physiology: Regulatory, Integrative and Comparative Physiology

IS - 9

ER -

Protection against high intravascular pressure in giraffe legs

Abstract

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