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Fukuda Y, Kawada T, Kataoka Y, Peterson J, Saku K, Alexander J, Sunagawa K. Influence of angiotensin II and telmisartan on in vivo high-resolution renal arterial impedance in rats. Am J Physiol Regul Integr Comp Physiol 2024; 327:R349-R361. [PMID: 39005079 DOI: 10.1152/ajpregu.00009.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Revised: 06/18/2024] [Accepted: 07/03/2024] [Indexed: 07/16/2024]
Abstract
Angiotensin II (ANG II) is known to play an important role in regulating renal hemodynamics. We sought to quantify this effect in an in vivo rat model with high-resolution renal arterial (RA) impedance. This study examines the effects of ANG II and its type 1 receptor blocker telmisartan (TELM) on RA impedance. In baroreflex-deactivated rats, we measured RA pressure (Pr) and blood flow (Fr) during random ventricular pacing to induce pressure fluctuation at three different mean Pr (60, 80, and 100 mmHg). We then estimated RA impedance as the transfer function from Fr to Pr. The RA impedance was found to align with a three-element Windkessel model consisting of proximal (Rp) and distal (Rd) resistance and compliance (C). Our study showed Rd reflected the composite characteristics of afferent and efferent arterioles. Rd increased with increasing Pr under the baseline condition with a slope of 1.03 ± 0.21 (× 10-1) min·mL-1. ANG II significantly increased the slope by 0.72 ± 0.29 (× 10-1) min·mL-1 (P < 0.05) without affecting the intercept. TELM significantly reduced the intercept by 34.49 ± 4.86 (× 10-1) mmHg·min·mL-1 (P < 0.001) from the baseline value of 37.93 ± 13.36 (× 10-1) mmHg·min·mL-1, whereas it did not affect the slope. In contrast, Rp was less sensitive than Rd to ANG II or TELM, suggesting Rp may represent the characteristics of elastic large arteries. Our findings provide valuable insights into the influence of ANG II on the dynamics of the renal vasculature.NEW & NOTEWORTHY This present method of quantifying high-resolution renal arterial impedance could contribute to elucidating the characteristics of renal vasculature influenced by physiological mechanisms, renal diseases, or pharmacological effects. The present findings help construct a lumped-parameter renal hemodynamic model that reflects the influence of angiotensin II.
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Affiliation(s)
- Yukiko Fukuda
- Medical and Health Informatics Laboratories, NTT Research, Inc., Sunnyvale, California, United States
| | - Toru Kawada
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, Japan
| | - Yasuyuki Kataoka
- Medical and Health Informatics Laboratories, NTT Research, Inc., Sunnyvale, California, United States
| | - Jon Peterson
- Medical and Health Informatics Laboratories, NTT Research, Inc., Sunnyvale, California, United States
| | - Keita Saku
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, Japan
- Bio Digital Twin Center, National Cerebral and Cardiovascular Center, Osaka, Japan
| | - Joe Alexander
- Medical and Health Informatics Laboratories, NTT Research, Inc., Sunnyvale, California, United States
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Kawada T, Li M, Nishiura A, Yoshida Y, Yokota S, Matsushita H, Fukumitsu M, Uemura K, Alexander J, Saku K. Acute effects of empagliflozin on open-loop baroreflex function and urinary glucose excretion in rats with chronic myocardial infarction. J Physiol Sci 2023; 73:20. [PMID: 37704939 DOI: 10.1186/s12576-023-00877-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2023] [Accepted: 09/04/2023] [Indexed: 09/15/2023]
Abstract
Sodium-glucose cotransporter 2 (SGLT2) inhibitors have exerted cardioprotective effects in clinical trials, but underlying mechanisms are not fully understood. As mitigating sympathetic overactivity is of major clinical concern in the mechanisms of heart failure treatments, we examined the effects of modulation of glucose handling on baroreflex-mediated sympathetic nerve activity and arterial pressure regulations in rats with chronic myocardial infarction (n = 9). Repeated 11-min step input sequences were used for an open-loop analysis of the carotid sinus baroreflex. An SGLT2 inhibitor, empagliflozin, was intravenously administered (10 mg/kg) after the second sequence. Neither the baroreflex neural nor peripheral arc significantly changed during the last observation period (seventh and eighth sequences) compared with the baseline period although urinary glucose excretion increased from near 0 (0.0089 ± 0.0011 mg min-1 kg-1) to 1.91 ± 0.25 mg min-1 kg-1. Hence, empagliflozin does not acutely modulate the baroreflex regulations of sympathetic nerve activity and arterial pressure in this rat model of chronic myocardial infarction.
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Affiliation(s)
- Toru Kawada
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, 564-8565, Japan.
| | - Meihua Li
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, 564-8565, Japan
| | - Akitsugu Nishiura
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, 564-8565, Japan
| | - Yuki Yoshida
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, 564-8565, Japan
| | - Shohei Yokota
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, 564-8565, Japan
| | - Hiroki Matsushita
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, 564-8565, Japan
| | - Masafumi Fukumitsu
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, 564-8565, Japan
| | - Kazunori Uemura
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, 564-8565, Japan
| | - Joe Alexander
- Medical and Health Informatics, NTT Research, Inc, Sunnyvale, CA, 94085, USA
| | - Keita Saku
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, 564-8565, Japan
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Kawada T, Yamamoto H, Yokoi A, Nishiura A, Kakuuchi M, Yokota S, Matsushita H, Alexander J, Saku K. Acute effects of empagliflozin on open-loop baroreflex function and urine glucose excretion in Goto-Kakizaki diabetic rats. J Physiol Sci 2023; 73:7. [PMID: 37046217 DOI: 10.1186/s12576-023-00861-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Accepted: 03/17/2023] [Indexed: 04/14/2023]
Abstract
Although suppression of sympathetic activity is suggested as one of the underlying mechanisms for the cardioprotective effects afforded by sodium-glucose cotransporter 2 (SGLT2) inhibitors, whether the modulation of glucose handling acutely affects sympathetic regulation of arterial pressure remains to be elucidated. In Goto-Kakizaki diabetic rats, we estimated the open-loop static characteristics of the carotid sinus baroreflex together with urine glucose excretion using repeated 11-min step input sequences. After the completion of the 2nd sequence, an SGLT2 inhibitor empagliflozin (10 mg kg-1) or vehicle solution was administered intravenously (n = 7 rats each). Empagliflozin did not significantly affect the baroreflex neural or peripheral arc, despite significantly increasing urine glucose excretion (from 0.365 ± 0.216 to 8.514 ± 0.864 mg·min-1·kg-1, P < 0.001) in the 7th and 8th sequences. The possible sympathoinhibitory effect of empagliflozin may be an indirect effect associated with chronic improvements in renal energy status and general disease conditions.
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Affiliation(s)
- Toru Kawada
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, 564-8565, Japan.
| | - Hiromi Yamamoto
- Department of Cardiovascular Medicine, Kurashiki Central Hospital, Ohara HealthCare Foundation, Okayama, 710-8602, Japan
| | - Aimi Yokoi
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, 564-8565, Japan
| | - Akitsugu Nishiura
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, 564-8565, Japan
| | - Midori Kakuuchi
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, 564-8565, Japan
| | - Shohei Yokota
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, 564-8565, Japan
| | - Hiroki Matsushita
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, 564-8565, Japan
| | - Joe Alexander
- Medical and Health Informatics, NTT Research, Inc., Sunnyvale, CA, 94085, USA
| | - Keita Saku
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, 564-8565, Japan
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Kawada T, Yokoi A, Nishiura A, Kakuuchi M, Li M, Uemura K, Suehara S, Sawada S, Saku K. Impact of neurally mediated antidiuretic effect relative to pressure diuresis during acute changes in sympathetic nerve activity. Am J Physiol Regul Integr Comp Physiol 2023; 324:R82-R89. [PMID: 36409023 DOI: 10.1152/ajpregu.00205.2022] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
We examined urine excretion during primary acute sympathetic activation (PASA) in anesthetized Wistar-Kyoto rats. Since arterial pressure (AP) changes with sympathetic nerve activity (SNA) during PASA, urine excretion reflects a neurally mediated antidiuretic effect combined with an effect of pressure diuresis. We hypothesized that preventing AP changes under PASA would enable the direct estimation of the neurally mediated antidiuretic effect alone. We changed the isolated carotid sinus pressure stepwise from 60 to 180 mmHg and compared the relationship of normalized urine flow (nUF, urine flow normalized by body weight) versus SNA between conditions allowing and preventing baroreflex-mediated changes in the mean AP. The slope of the SNA-nUF relationship was [Formula: see text]nUFvar = 0.444 ± 0.074 μL·min-1·kg-1·%-1 when the mean AP was variable, whereas it was [Formula: see text]nUFfix = -0.143 ± 0.032 μL·min-1·kg-1·%-1 when the mean AP was fixed at 100 mmHg (n = 7 rats). The slope associated with the effect of pressure diuresis alone, calculated as [Formula: see text]nUFvar - [Formula: see text]nUFfix, was 0.586 ± 0.105 μL·min-1·kg-1·%-1. Hence, the potency of the neurally mediated antidiuretic effect |[Formula: see text]nUFfix|/([Formula: see text]nUFvar - [Formula: see text]nUFfix) was 0.235 ± 0.014 relative to the effect of pressure diuresis under PASA. Our findings would aid an integrative understanding of the effects of renal hemodynamic and sympathetic modulations on urine output function.
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Affiliation(s)
- Toru Kawada
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Suita, Japan
| | - Aimi Yokoi
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Suita, Japan
| | - Akitsugu Nishiura
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Suita, Japan
| | - Midori Kakuuchi
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Suita, Japan
| | - Meihua Li
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Suita, Japan
| | - Kazunori Uemura
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Suita, Japan
| | | | | | - Keita Saku
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Suita, Japan
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Angiotensin II inhibition increases diuresis during acute sympathetic activation in intact and denervated kidneys in rats with chronic myocardial infarction. Heart Vessels 2022; 37:1636-1646. [PMID: 35689098 DOI: 10.1007/s00380-022-02110-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Accepted: 05/25/2022] [Indexed: 11/04/2022]
Abstract
We examined urine excretion during primary acute sympathetic activation (PASA) in Wistar-Kyoto rats with myocardial infarction (MI). The rats underwent unilateral renal denervation (RDN) 7 weeks after coronary artery ligation. 4-10 days later, an acute experiment was performed under anesthetized conditions (n = 8 rats). Isolated carotid sinus pressure was changed stepwise from 60 to 180 mmHg, and the relationship between the arterial pressure (AP) and the normalized urine flow (nUF, urine flow normalized by the body weight) was examined. After obtaining the control data, an angiotensin II type 1 receptor blocker telmisartan (2.5 mg/kg) was intravenously administered. The effects of RDN, telmisartan, and heart weight (biventricular weight) on the relationship between AP and nUF were examined using multiple regression analyses. Regarding the slope of nUF versus AP (nUFslope), the constant term of the regression was positive (0.315 ± 0.069 μL·min-1·kg-1·mmHg-1), indicating that nUF increased with AP. The heart weight had a negative effect on nUFslope (P < 0.05), suggesting that the severity of MI was associated with the impairment of urine excretion. Telmisartan increased nUFslope by 0.358 ± 0.080 μL·min-1·kg-1·mmHg-1 (P < 0.001), whereas RDN had no significant effect on this parameter. The results indicate that unilateral RDN was unable to abolish the effect of the renin-angiotensin system on urine excretion during PASA. Circulating or locally produced angiotensin II, rather than ongoing renal sympathetic nerve activity, played a dominant role in the impairment of urine excretion during PASA in rats with chronic MI.
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