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Comparative study between heart and kidney microcirculations
Materials Science and Engineering C 13 Ž2000. 3–6 www.elsevier.comrlocatermsec
Comparative study between heart and kidney microcirculations Microvisualization approach Fumihiko Kajiya Kawasaki Medical School, Kurashiki, Okayama 701-0192, Japan
Abstract Comparative study between heart and kidney microcirculations was made by a microvisualization technique. To visualize Ži. the subendocardial microcirculation and Žii. intrarenal microcirculation Žespecially afferent and efferent arterioles., we developed a needle–lens probe videomicroscope Žmagnification: 200–400.. To observe subendocardial arterioles, we introduced the needle–lens probe Ž4 mm. onto endocardial surface through the mitral valve from a small incision at the left atrial appendage in dogs. The diameter of subendomyocardial arterioles changed during a cardiac cycle by about 20%, while the change in subepicardial arteriolar diameter was almost negligible. The subendocardial blood flow velocity waveform visualized by a light marker exhibited an exclusively diastolic pattern with reverse flow during systole, while the subepicardial flow direction was forward through a cardiac cycle. To visualize the intrarenal microcirculation, we inserted the cone-shaped needle–lens into kidney directly from the renal capsule in normal ŽWKY., spontaneous hypertensive rats ŽSHR., and streptozosin induced diabetic rats ŽSTZ.. The afferent and efferent arteriolar sizes in WKY were nearly equal, i.e., 12 and 9 mm, respectively; however, the afferent arteriolar size in SHR was smaller Žabout 60% of WKY. and that in STZ was larger Ž120% of WKY.. The diameters of efferent arterioles in both SHR and STZ were similar to WKY. In conclusion, the microcirculations in the heart and kidney are of different dynamic behaviors: Ži. with motion including diameter change and Aslosh phenomenonB of flow waveform in the heart and Žii. without dynamic motion, but delicate vasomotor tone control of afferent and efferent arterioles in the kidney. q 2000 Elsevier Science S.A. All rights reserved. Keywords: Heart; Kidney; Microvisualization technique
1. Introduction The microcirculations in the two important vital organs, i.e., the heart and kidney are of quite different characters: dynamic behaviors with motion in the heart and without motion in the kidney. The blood supply to both organs is rich; under physiological conditions, the heart muscle receives 5% blood of the total cardiac output and the two kidneys, 20%. From pathophysiological viewpoints, in the heart, the microcirculation in the deeper portion Žsubendocardium. is especially important because of its higher vulnerability to ischemia, while in the kidney, the afferent and efferent arterioles of the glomerulus play a crucial role by controlling glomerular capillary pressure for urine filtration. In this paper, a comparative study between the heart and kidney microcirculations using an intravital microscope is presented mainly by focusing on their microvascular dynamic behaviors.
2. Novel needle-probe CCD microscope for visualization of the microcirculations in the heart and kidney To visualize both superficial and deeper microcirculation, we have developed an intravital videomicroscope w1–5x. The system consists of a needle probe, a camera body equipped with a CCD camera, a lens and light guides, a control unit, a light source, a monitor and a videocassette recorder ŽVCR. ŽFig. 1.. The needle probe Ždiameter: 1–4 mm, length: several ; 18 cm. contains a gradient-index lens surrounded by 18 annular optical-fiber light guides. The tissue was illuminated by a halogen lump Ž150 W. through a green filter to accentuate the contrast between vessels and surrounding tissue. The back-scattered light from the tissue visualizes the vascular image inside the organs. The spatial resolution of this system is about 1.0–2.0 mm and the temporal resolution is 30–200 im-
0928-4931r00r$ - see front matter q 2000 Elsevier Science S.A. All rights reserved. PII: S 0 9 2 8 - 4 9 3 1 Ž 0 0 . 0 0 1 6 9 - 7
4
F. Kajiyar Materials Science and Engineering C 13 (2000) 3–6
Fig. 1. Needle Žlens.-probe CCD videomicroscope.
agesrs. The system was modified in the visualization of different organs.
3. The heart microcirculation: unique subendocardial (deeper portion) hemodynamics during a cardiac cycle To visualize the microcirculation in the deeper portion of the heart Žsubendocardium. which had not been possible, the needle probe was inserted from the left atrium Ždogs or pigs. and introduced onto the endocardial surface through the mitral valve. The doughnut-shaped balloon surrounding the needle tip was then inflated not to compress the microvessels directly with the probe. The blood
between the needle tip and the endocardium was flushed away with a buffer solution through a small tubule to obtain a clear image. Fig. 2A shows an image of niobium microspheres to trace blood velocities in the microcirculation of the subendocardium at end-diastole w6x. The blood velocities during a cardiac cycle were calculated by monitoring the moving distance of microspheres every 5 ms. The vascular diameter was also measured every 30 ms during the same cardiac cycle. Fig. 2B shows a typical example of a blood velocity waveform in the subendocardial arteriole that exhibited velocity waveforms quite different from other organs including kidney, i.e., forward flow exclusively during diastole and reverse flow during systole. The blood velocity in the superficial layer Žepi-
Fig. 2. Visualization of the subendocardial arteriole with blood flow light markers.
F. Kajiyar Materials Science and Engineering C 13 (2000) 3–6
5
Fig. 3. Schematic drawings of afferent and efferent arteriolar diameters among control, spontaneous hypertensive rats ŽSHR., and streptozosin induced diabetic rats ŽSTZ.. Smaller afferent arteriolar diameter was noticed in SHR but larger one was in STZ rats compared with normal rats. The efferent arteriolar diameters were similar among normal, SHR, and STZ rats.
cardium., in contrast, exhibited forward flow during systole like other organs, while the diastolic flow was similar between the endocardium and epicardium w7x. The vascular diameter of endocardium was decreased by about 20% ŽFig. 2C. during systole while that in the epicardium changed slightly throughout a cardiac cycle. The systolic narrowing in the midlayer was similar to that in the endocardium. It is indicated that this unique flow pattern in the endocardium and midcardium is caused by diastolic relaxation and systolic compression of the microvessels by the heart motion. The unique velocity waveform implies that part of stored blood in the subendocardium during diastole flowed backward during the following systole. We called this systolic wasteful reverse flow as Acoronary slosh phenomenonB w8x. This coronary slosh is important to understand the mechanism for the clinically well known higher incidence of ischemia in the subendomyocardium.
4. The kidney microcirculation: visualization of afferent and efferent arterioles To visualize the intrarenal microcirculation, we modified our system as a tapered-tip type using a cone-type lens w9x. The specifications are as follows: tip diameters 1 mmf, magnifications 520-power, spatial resolutions 0.86 mm. The left kidney of each rat was isolated from the surrounding tissues, and the renal capsule with less vascular network was cut Žlengths 1 mm, depth s 0.3 mm.. The cone-type lens probe was inserted at the cut point and was moved so as to obtain clear image of glomerulus with afferent and efferent arterioles. When good images of afferent and efferent arterioles were obtained, the probe was pulled back several tens of micrometers to minimize the effect of needle introduction. This method is very useful physiologically because the tubuloglomerular feed-
back ŽTGF. mechanism is intact in this setup, i.e., 25% hypertonic saline infusion to the renal artery caused constriction of the afferent arterioles by TGF. Fig. 3a shows a sketch of microimage of a normal ŽWKY. rat. Fig. 3b and c illustrated the images from male SHR and STZ. The afferent and efferent arterioles are nearly equal in size in the normal rats, i.e., 12 and 9 mm, respectively. However, the afferent arterioles are very small in the SHR Žabout 60% of WKY., while the efferent arteriolar size was similar to WKY. In the STZ rats, the afferent arteriole was large Žabout 120% of WKY. with a similar efferent arteriolar size. Blood pressure was similar between WKY and STZ, while that of SHR was elevated by 80%. Blood glucose was elevated only in STZ rats Žthree-fold increase from WKY and SHR.. It is postulated that the glomerular capillary pressure of SHR is maintained to almost normal value in spite of high blood pressure. The vasoconstriction of afferent arterioles in SHR may be a major factor keeping the pressure normal, probably by involvement of control mechanism such as glomerulo-tubular feedback mechanism and myogenic mechanism. It is well known that the hyperfiltration is an initial mechanism to induce diabetic nephropathy. Our observation of the enlarged afferent arterioles may play a key role of causing glomerular hyperfiltration by elevating the capillary pressure there.
5. Concluding remarks We demonstrated unique microvascular hemodynamics in the heart Žslosh phenomenon with diameter changes. and in the kidney Žrelative diameter changes between afferent and efferent arterioles to control glomerular capillary pressure and flow. by our novel intravital microscope.
6
F. Kajiyar Materials Science and Engineering C 13 (2000) 3–6
Acknowledgements The author thanks Drs. Yasuo Ogasawara, Toyotaka Yada, Osamu Hiramatsu, Eiji Toyota and Mr. Hiroyuki Tachibana for the heart study; Drs. Tokunori Yamamoto, Hiroshi Nakamoto, and Yuichi Tomura for the renal study; and Ms. Chikako Tokuda for her secretarial work. This study was supported in part by grant-in-aid 09480529 and 10558140 for Scientific Research from the Ministry of Education, Science, Sports and Culture, Japan.
w4x
w5x
w6x
References w7x w1x T. Yada, O. Hiramatsu, A. Kimura, M. Goto, Y. Ogasawara, K. Tsujioka, S. Yamamori, K. Ohno, H. Hosaka, F. Kajiya, In vivo observation of subendocardial microvessels of the beating porcine heart using a needle-probe video-microscope with a CCD camera, Circ. Res. 72 Ž1993. 939–946. w2x T. Yada, O. Hiramatsu, A. Kimura, H. Tachibana, Y. Chiba, S. Lu, M. Goto, Y. Ogasawara, K. Tsujioka, F. Kajiya, Direct in vivo observation of subendocardial arteriolar response during reactive hyperemia, Circ. Res. 77 Ž1995. 622–631. w3x O. Hiramatsu, M. Goto, T. Yada, A. Kimura, H. Tachibana, Y.
w8x
w9x
Ogasawara, K. Tsujioka, F. Kajiya, Diameters of subendocardial arterioles and venules during prolonged diastoles in canine left ventricles, Circ. Res. 75 Ž1994. 393–399. O. Hiramatsu, M. Goto, T. Yada, A. Kimura, Y. Chiba, H. Tachibana, Y. Ogasawara, K. Tsujioka, F. Kajiya, In-vivo observation of the intramural arterioles and venules in beating canine hearts, J. Physiol. 509 Ž2. Ž1998. 619–627. F. Kajiya, Y. Ogasawara, O. Hiramatsu, H. Tachibana, M. Goto, T. Yada, The relationship between cardiac contraction and intramyocardial hemodynamics — new tools for analyzing the coronary venous system-Žinvited., IEEE Eng. Med. Biol. 16 Ž5. Ž1997. 127–132. F. Kajiya, Temporal and spatial heterogeneity of blood supply to the heart-visualization and -interpretation, Proceedings of the 2nd IMIAIFMBE International Workshop on Biosignal Interpretation 1996, pp. 1–4. E. Toyota, M. Goto, H. Nakamoto, J. Ebata, H. Tachibana, O. Hiramatsu, Y. Ogasawara, F. Kajiya, Endothelium-derived nitric oxide enhances the effect of IABP on diastolic coronary flow, Ann. Thorac. Surg. 67 Ž5. Ž1999. 1254–1261. A. Kimura, O. Hiramatsu, T. Yamamoto, Y. Ogasawara, T. Yada, M. Goto, K. Tsujioka, F. Kajiya, Effect of coronary stenosis on phasic pattern of septal artery in the dog, Am. J. Physiol. 262 Ž1992. H1690–H1698. T. Yamamoto, K. Hayashi, Y. Yomura, F. Kajiya, Direct in vivo visualization of renal microcirculation by intravital CCD videomicroscopy, Exp. Nephrol. 18 Ž4. Ž2000. .
Comparative study between heart and kidney microcirculations Microvisualization approach Fumihiko Kajiya Kawasaki Medical School, Kurashiki, Okayama 701-0192, Japan
Abstract Comparative study between heart and kidney microcirculations was made by a microvisualization technique. To visualize Ži. the subendocardial microcirculation and Žii. intrarenal microcirculation Žespecially afferent and efferent arterioles., we developed a needle–lens probe videomicroscope Žmagnification: 200–400.. To observe subendocardial arterioles, we introduced the needle–lens probe Ž4 mm. onto endocardial surface through the mitral valve from a small incision at the left atrial appendage in dogs. The diameter of subendomyocardial arterioles changed during a cardiac cycle by about 20%, while the change in subepicardial arteriolar diameter was almost negligible. The subendocardial blood flow velocity waveform visualized by a light marker exhibited an exclusively diastolic pattern with reverse flow during systole, while the subepicardial flow direction was forward through a cardiac cycle. To visualize the intrarenal microcirculation, we inserted the cone-shaped needle–lens into kidney directly from the renal capsule in normal ŽWKY., spontaneous hypertensive rats ŽSHR., and streptozosin induced diabetic rats ŽSTZ.. The afferent and efferent arteriolar sizes in WKY were nearly equal, i.e., 12 and 9 mm, respectively; however, the afferent arteriolar size in SHR was smaller Žabout 60% of WKY. and that in STZ was larger Ž120% of WKY.. The diameters of efferent arterioles in both SHR and STZ were similar to WKY. In conclusion, the microcirculations in the heart and kidney are of different dynamic behaviors: Ži. with motion including diameter change and Aslosh phenomenonB of flow waveform in the heart and Žii. without dynamic motion, but delicate vasomotor tone control of afferent and efferent arterioles in the kidney. q 2000 Elsevier Science S.A. All rights reserved. Keywords: Heart; Kidney; Microvisualization technique
1. Introduction The microcirculations in the two important vital organs, i.e., the heart and kidney are of quite different characters: dynamic behaviors with motion in the heart and without motion in the kidney. The blood supply to both organs is rich; under physiological conditions, the heart muscle receives 5% blood of the total cardiac output and the two kidneys, 20%. From pathophysiological viewpoints, in the heart, the microcirculation in the deeper portion Žsubendocardium. is especially important because of its higher vulnerability to ischemia, while in the kidney, the afferent and efferent arterioles of the glomerulus play a crucial role by controlling glomerular capillary pressure for urine filtration. In this paper, a comparative study between the heart and kidney microcirculations using an intravital microscope is presented mainly by focusing on their microvascular dynamic behaviors.
2. Novel needle-probe CCD microscope for visualization of the microcirculations in the heart and kidney To visualize both superficial and deeper microcirculation, we have developed an intravital videomicroscope w1–5x. The system consists of a needle probe, a camera body equipped with a CCD camera, a lens and light guides, a control unit, a light source, a monitor and a videocassette recorder ŽVCR. ŽFig. 1.. The needle probe Ždiameter: 1–4 mm, length: several ; 18 cm. contains a gradient-index lens surrounded by 18 annular optical-fiber light guides. The tissue was illuminated by a halogen lump Ž150 W. through a green filter to accentuate the contrast between vessels and surrounding tissue. The back-scattered light from the tissue visualizes the vascular image inside the organs. The spatial resolution of this system is about 1.0–2.0 mm and the temporal resolution is 30–200 im-
0928-4931r00r$ - see front matter q 2000 Elsevier Science S.A. All rights reserved. PII: S 0 9 2 8 - 4 9 3 1 Ž 0 0 . 0 0 1 6 9 - 7
4
F. Kajiyar Materials Science and Engineering C 13 (2000) 3–6
Fig. 1. Needle Žlens.-probe CCD videomicroscope.
agesrs. The system was modified in the visualization of different organs.
3. The heart microcirculation: unique subendocardial (deeper portion) hemodynamics during a cardiac cycle To visualize the microcirculation in the deeper portion of the heart Žsubendocardium. which had not been possible, the needle probe was inserted from the left atrium Ždogs or pigs. and introduced onto the endocardial surface through the mitral valve. The doughnut-shaped balloon surrounding the needle tip was then inflated not to compress the microvessels directly with the probe. The blood
between the needle tip and the endocardium was flushed away with a buffer solution through a small tubule to obtain a clear image. Fig. 2A shows an image of niobium microspheres to trace blood velocities in the microcirculation of the subendocardium at end-diastole w6x. The blood velocities during a cardiac cycle were calculated by monitoring the moving distance of microspheres every 5 ms. The vascular diameter was also measured every 30 ms during the same cardiac cycle. Fig. 2B shows a typical example of a blood velocity waveform in the subendocardial arteriole that exhibited velocity waveforms quite different from other organs including kidney, i.e., forward flow exclusively during diastole and reverse flow during systole. The blood velocity in the superficial layer Žepi-
Fig. 2. Visualization of the subendocardial arteriole with blood flow light markers.
F. Kajiyar Materials Science and Engineering C 13 (2000) 3–6
5
Fig. 3. Schematic drawings of afferent and efferent arteriolar diameters among control, spontaneous hypertensive rats ŽSHR., and streptozosin induced diabetic rats ŽSTZ.. Smaller afferent arteriolar diameter was noticed in SHR but larger one was in STZ rats compared with normal rats. The efferent arteriolar diameters were similar among normal, SHR, and STZ rats.
cardium., in contrast, exhibited forward flow during systole like other organs, while the diastolic flow was similar between the endocardium and epicardium w7x. The vascular diameter of endocardium was decreased by about 20% ŽFig. 2C. during systole while that in the epicardium changed slightly throughout a cardiac cycle. The systolic narrowing in the midlayer was similar to that in the endocardium. It is indicated that this unique flow pattern in the endocardium and midcardium is caused by diastolic relaxation and systolic compression of the microvessels by the heart motion. The unique velocity waveform implies that part of stored blood in the subendocardium during diastole flowed backward during the following systole. We called this systolic wasteful reverse flow as Acoronary slosh phenomenonB w8x. This coronary slosh is important to understand the mechanism for the clinically well known higher incidence of ischemia in the subendomyocardium.
4. The kidney microcirculation: visualization of afferent and efferent arterioles To visualize the intrarenal microcirculation, we modified our system as a tapered-tip type using a cone-type lens w9x. The specifications are as follows: tip diameters 1 mmf, magnifications 520-power, spatial resolutions 0.86 mm. The left kidney of each rat was isolated from the surrounding tissues, and the renal capsule with less vascular network was cut Žlengths 1 mm, depth s 0.3 mm.. The cone-type lens probe was inserted at the cut point and was moved so as to obtain clear image of glomerulus with afferent and efferent arterioles. When good images of afferent and efferent arterioles were obtained, the probe was pulled back several tens of micrometers to minimize the effect of needle introduction. This method is very useful physiologically because the tubuloglomerular feed-
back ŽTGF. mechanism is intact in this setup, i.e., 25% hypertonic saline infusion to the renal artery caused constriction of the afferent arterioles by TGF. Fig. 3a shows a sketch of microimage of a normal ŽWKY. rat. Fig. 3b and c illustrated the images from male SHR and STZ. The afferent and efferent arterioles are nearly equal in size in the normal rats, i.e., 12 and 9 mm, respectively. However, the afferent arterioles are very small in the SHR Žabout 60% of WKY., while the efferent arteriolar size was similar to WKY. In the STZ rats, the afferent arteriole was large Žabout 120% of WKY. with a similar efferent arteriolar size. Blood pressure was similar between WKY and STZ, while that of SHR was elevated by 80%. Blood glucose was elevated only in STZ rats Žthree-fold increase from WKY and SHR.. It is postulated that the glomerular capillary pressure of SHR is maintained to almost normal value in spite of high blood pressure. The vasoconstriction of afferent arterioles in SHR may be a major factor keeping the pressure normal, probably by involvement of control mechanism such as glomerulo-tubular feedback mechanism and myogenic mechanism. It is well known that the hyperfiltration is an initial mechanism to induce diabetic nephropathy. Our observation of the enlarged afferent arterioles may play a key role of causing glomerular hyperfiltration by elevating the capillary pressure there.
5. Concluding remarks We demonstrated unique microvascular hemodynamics in the heart Žslosh phenomenon with diameter changes. and in the kidney Žrelative diameter changes between afferent and efferent arterioles to control glomerular capillary pressure and flow. by our novel intravital microscope.
6
F. Kajiyar Materials Science and Engineering C 13 (2000) 3–6
Acknowledgements The author thanks Drs. Yasuo Ogasawara, Toyotaka Yada, Osamu Hiramatsu, Eiji Toyota and Mr. Hiroyuki Tachibana for the heart study; Drs. Tokunori Yamamoto, Hiroshi Nakamoto, and Yuichi Tomura for the renal study; and Ms. Chikako Tokuda for her secretarial work. This study was supported in part by grant-in-aid 09480529 and 10558140 for Scientific Research from the Ministry of Education, Science, Sports and Culture, Japan.
w4x
w5x
w6x
References w7x w1x T. Yada, O. Hiramatsu, A. Kimura, M. Goto, Y. Ogasawara, K. Tsujioka, S. Yamamori, K. Ohno, H. Hosaka, F. Kajiya, In vivo observation of subendocardial microvessels of the beating porcine heart using a needle-probe video-microscope with a CCD camera, Circ. Res. 72 Ž1993. 939–946. w2x T. Yada, O. Hiramatsu, A. Kimura, H. Tachibana, Y. Chiba, S. Lu, M. Goto, Y. Ogasawara, K. Tsujioka, F. Kajiya, Direct in vivo observation of subendocardial arteriolar response during reactive hyperemia, Circ. Res. 77 Ž1995. 622–631. w3x O. Hiramatsu, M. Goto, T. Yada, A. Kimura, H. Tachibana, Y.
w8x
w9x
Ogasawara, K. Tsujioka, F. Kajiya, Diameters of subendocardial arterioles and venules during prolonged diastoles in canine left ventricles, Circ. Res. 75 Ž1994. 393–399. O. Hiramatsu, M. Goto, T. Yada, A. Kimura, Y. Chiba, H. Tachibana, Y. Ogasawara, K. Tsujioka, F. Kajiya, In-vivo observation of the intramural arterioles and venules in beating canine hearts, J. Physiol. 509 Ž2. Ž1998. 619–627. F. Kajiya, Y. Ogasawara, O. Hiramatsu, H. Tachibana, M. Goto, T. Yada, The relationship between cardiac contraction and intramyocardial hemodynamics — new tools for analyzing the coronary venous system-Žinvited., IEEE Eng. Med. Biol. 16 Ž5. Ž1997. 127–132. F. Kajiya, Temporal and spatial heterogeneity of blood supply to the heart-visualization and -interpretation, Proceedings of the 2nd IMIAIFMBE International Workshop on Biosignal Interpretation 1996, pp. 1–4. E. Toyota, M. Goto, H. Nakamoto, J. Ebata, H. Tachibana, O. Hiramatsu, Y. Ogasawara, F. Kajiya, Endothelium-derived nitric oxide enhances the effect of IABP on diastolic coronary flow, Ann. Thorac. Surg. 67 Ž5. Ž1999. 1254–1261. A. Kimura, O. Hiramatsu, T. Yamamoto, Y. Ogasawara, T. Yada, M. Goto, K. Tsujioka, F. Kajiya, Effect of coronary stenosis on phasic pattern of septal artery in the dog, Am. J. Physiol. 262 Ž1992. H1690–H1698. T. Yamamoto, K. Hayashi, Y. Yomura, F. Kajiya, Direct in vivo visualization of renal microcirculation by intravital CCD videomicroscopy, Exp. Nephrol. 18 Ž4. Ž2000. .