Evidence That Binding of Cyclic GMP to the Extracellular Domain of NKA (Sodium-Potassium ATPase) Mediates Natriuresis.

BACKGROUND: Extracellular renal interstitial guanosine cyclic 3',5'-monophosphate (cGMP) inhibits renal proximal tubule (RPT) sodium (Na+) reabsorption via Src (Src family kinase) activation. Through which target extracellular cGMP acts to induce natriuresis is unknown. We hypothesized that cGMP binds to the extracellular α1-subunit of NKA (sodium-potassium ATPase) on RPT basolateral membranes to inhibit Na+ transport similar to ouabain-a cardiotonic steroid. METHODS: Urine Na+ excretion was measured in uninephrectomized 12-week-old female Sprague-Dawley rats that received renal interstitial infusions of vehicle (5% dextrose in water), cGMP (18, 36, and 72 µg/kg per minute; 30 minutes each), or cGMP+rostafuroxin (12 ng/kg per minute) or were subjected to pressure-natriuresis±rostafuroxin infusion. Rostafuroxin is a digitoxigenin derivative that displaces ouabain from NKA. RESULTS: Renal interstitial cGMP and raised renal perfusion pressure induced natriuresis and increased phosphorylated SrcTyr416 and Erk 1/2 (extracellular signal-regulated protein kinase 1/2)Thr202/Tyr204; these responses were abolished with rostafuroxin coinfusion. To assess cGMP binding to NKA, we performed competitive binding studies with isolated rat RPTs using bodipy-ouabain (2 µM)+cGMP (10 µM) or rostafuroxin (10 µM) and 8-biotin-11-cGMP (2 µM)+ouabain (10 µM) or rostafuroxin (10 µM). cGMP or rostafuroxin reduced bodipy-ouabain fluorescence intensity, and ouabain or rostafuroxin reduced 8-biotin-11-cGMP staining. We cross-linked isolated rat RPTs with 4-N3-PET-8-biotin-11-cGMP (2 µM); 8-N3-6-biotin-10-cAMP served as negative control. Precipitation with streptavidin beads followed by immunoblot analysis showed that RPTs after cross-linking with 4-N3-PET-8-biotin-11-cGMP exhibited a significantly stronger signal for NKA than non-cross-linked samples and cross-linked or non-cross-linked 8-N3-6-biotin-10-cAMP RPTs. Ouabain (10 µM) reduced NKA in cross-linked 4-N3-PET-8-biotin-11-cGMP RPTs confirming fluorescence staining. 4-N3-PET-8-biotin-11-cGMP cross-linked samples were separated by SDS gel electrophoresis and slices corresponding to NKA molecular weight excised and processed for mass spectrometry. NKA was the second most abundant protein with 50 unique NKA peptides covering 47% of amino acids in NKA. Molecular modeling demonstrated a potential cGMP docking site in the ouabain-binding pocket of NKA. CONCLUSIONS: cGMP can bind to NKA and thereby mediate natriuresis.

Renal AT2 Receptors Mediate Natriuresis via Protein Phosphatase PP2A.

BACKGROUND: How signals from activated angiotensin type-2 receptors (AT2R) mediate inhibition of sodium ion (Na+) reabsorption in renal proximal tubule cells is currently unknown. Protein phosphatases including PP2A (protein phosphatase 2A) have been implicated in AT2R signaling in tissues other than kidney. We investigated whether inhibition of protein phosphatase PP2A reduced AT2R-mediated natriuresis and evaluated changes in PP2A activity and localization after renal AT2R activation in normal 4- and 10-week-old control Wistar-Kyoto rats and 4-week-old prehypertensive and 10-week-old hypertensive spontaneously hypertensive rats. METHODS AND RESULTS: In Wistar-Kyoto rats, direct renal interstitial administration of selective AT2R nonpeptide agonist Compound-21 (C-21) increased renal interstitial cyclic GMP (cGMP) levels, urine Na+ excretion, and simultaneously increased PP2A activity ≈2-fold in homogenates of renal cortical tubules. The cyclic GMP and natriuretic responses were abolished by concurrent renal interstitial administration of protein phosphatase inhibitor calyculin A. In renal proximal tubule cells in response to C-21, PP2A subunits A, B55α and C, but not B56γ, were recruited to apical plasma membranes together with AT2Rs. Calyculin A treatment abolished C-21-induced translocation of both AT2R and PP2A regulatory subunit B55α to apical plasma membranes. Immunoprecipitation of AT2R solubilized from renal cortical homogenates demonstrated physical association of AT2R with PP2A A, B55α, and C but not B56γ subunits. In contrast, in spontaneously hypertensive rats, administration of C-21 did not alter urine Na+ excretion or PP2A activity and failed to translocate AT2Rs and PP2A subunits to apical plasma membranes. CONCLUSIONS: In renal proximal tubule cells of Wistar-Kyoto rats, PP2A is activated and PP2A subunits AB55αC are recruited to C-21-activated AT2Rs during induction of natriuresis. This response is defective in prehypertensive and hypertensive spontaneously hypertensive rats, presenting a potential novel therapeutic target for treating renal Na+ retention and hypertension.

Age as a Factor in Diversity, Equity, and Inclusion Initiatives in Higher Education.

Demographic shifts and the growth of diversity, equity, and inclusion (DEI) initiatives are occurring simultaneously on college campuses. This study seeks to understand their intersection by focusing on age in DEI initiatives on college campuses. Findings from six focus groups suggest that age is not given much attention in DEI initiatives. Participants acknowledge the issue of age; but in general, they strive to keep other identities, like race and gender, in the forefront, especially in the face of low resources. While it may be difficult to elevate age in DEI initiatives on campuses, interventions were identified.

Anti-Ageism for Gerontologists.

We argue that gerontologists are products of our ageist culture and that we both perpetuate ageism and suffer from internalized ageism ourselves. We make ageist comments, deny our own age, fail to teach students to recognize and confront ageism, and use language that otherizes and categorizes older people. Gerontologists are in ideal positions to confront ageism through our scholarly work, teaching, and community engagement. However, we suggest that, despite our deep gerontological knowledge, we do not have enough awareness, knowledge, and skills for taking anti-ageism actions in these arenas of our professional lives. We offer some suggestions for confronting ageism, including self-study, increasing content on ageism in the classroom and beyond, pointing out ageist language and behaviors to colleagues and students, working with diversity, equity and inclusion offices on campus, and giving careful consideration to our research approaches and academic writing. To go forward, we must increase awareness about ageism and gain skills in promoting anti-ageism.

Pandemic Pivots for Older Volunteers: Online Tutoring and Pen Pal Programs.

This study explored the experiences of older adult volunteers who pivoted from in-person tutoring to letter writing and online tutoring during the COVID-19 pandemic. Sixty-one older adult volunteers were surveyed in the beginning and end of the school year about their experiences, including their perceived benefits, challenges, and feedback on the pandemic transition. Eleven of the surveyed volunteers participated in focus groups at the end of the school year. Perceived benefits included having a positive impact on a child's life and meaningful engagement during the pandemic, and perceived challenges included difficulty engaging students and lack of control over learning environments. The participants also suggested increasing opportunities for informal interactions with staff and students, technology training, and peer support between volunteers. There was agreement that the remote volunteering experience was not a substitute for in-person tutoring, but it was better than no volunteering at all.

Situating the Pandemic in the Life-Course: Older Adults' Perspectives on the Challenges and Positives of the COVID-19 Pandemic.

Older adults experienced the highest rates of infections and deaths and significant social isolation during the COVID-19 pandemic. While these negative impacts are important to address, the positive outcomes among older adults during the pandemic are equally important. A survey was distributed to adults aged 65 or older living in St. Louis, Missouri from August 2020 through March 2021 to characterize the challenges and positives they found during the pandemic. A total of 103 older adults participated. Compared to previous times in their lives, a majority of participants felt the pandemic had been more disruptive (62%) and more confusing (78%) and a majority were more worried (58%) and more afraid of dying (53%) during the pandemic. The most common positives were increased emotional well-being (23% of responses) and stronger personal connections (20% of responses). This ability to identify positive outcomes of the pandemic demonstrates the resilience of older adults and counters the ageist narrative that dominated the dialogue early in the pandemic, which depicted older adults as weak, vulnerable, and dispensable. As the pandemic evolves, nurturing and leveraging these positives will be key to combatting the cycle of fear and restrictions that the pandemic could bring.

Civic Activities and Mental Health in Later Life: The Moderating Role of Generative Concerns.

This study examined the moderating mechanisms of generative concerns (perception of making contributions to others) between generative civic activities and mental health among middle-aged and older adults. A total of 1,109 community-dwelling adults aged over 45 were recruited through an online survey. Generative civic activities (political participation and volunteering), generative concerns (the Loyola Generativity Scale), and two outcomes of mental health (depressive symptoms and mental wellbeing) were measured. Linear regression models and simple slope analyses were used to probe the moderating effects of generative concerns, stratified by age (45-64 years and 65+). Generative activities, but not concerns, were associated with lower depressive symptoms among middle-aged and older adults. Generative concerns and activities were related to better mental wellbeing among middle-aged adults. Generative concerns moderated the associations between civic activities and depressive symptoms. Those with higher generative concerns but lower civic activities had higher depression scores. Conversely, a stronger reduction in depressive symptoms by engaging in civic activities was found only when individuals had greater concerns. No moderating effect was found on mental wellbeing. The positive effect of civic engagement on reducing depressive symptoms depends on generative concerns, particularly among older people and those with greater concerns. Bridging the gap between perceived generative concerns and actual civic actions may improve later-life mental health.

Deaths of Despair and Population Aging in Missouri.

Recent declines in life expectancy in the US, especially for middle-aged White persons, have called attention to mortality from deaths of despair - deaths due to alcohol, drugs, and suicide. Using data from the Centers for Disease Control and the U.S. Census Bureau, this paper examined deaths of despair by race/ethnicity, age, cause of death, birth cohort, and sex in Missouri. We focused on Area Agencies on Aging as geographic units of interest to increase usefulness of our findings to public administrators. Deaths of despair began trending up for all age groups beginning in 2007-2009, with the sharpest increases occurring for Black or African American non-Hispanics beginning in 2013-2015. The most dramatic increases occurred for the population age 50-59 in St. Louis City and Area Agency on Aging regions in southern Missouri. For older adults, considerable variation in rates, trends, and cause of deaths of despair is evident across the state.

Identification of a Primary Renal AT2 Receptor Defect in Spontaneously Hypertensive Rats.

RATIONALE: Previous studies identified a defect in Ang III (angiotensin III [des-aspartyl1-angiotensin II])-elicited AT2R (Ang type-2 receptor)-mediated natriuresis in renal proximal tubule cells of spontaneously hypertensive rats (SHR). OBJECTIVE: This study aimed to delineate in prehypertensive SHR kidneys the receptor or postreceptor defect causing impaired AT2R signaling and renal sodium (Na+) retention by utilizing the selective AT2R agonist compound-21 (C-21). METHODS AND RESULTS: Female 4-week-old Wistar Kyoto and SHR rats were studied after 24-hour systemic AT1R (Ang II type-1 receptor) blockade. Left kidneys received 30-minute renal interstitial infusions of vehicle followed by C-21 (20, 40, and 60 ng/[kg·min], each dose 30 minutes). Right kidneys received vehicle infusions. In Wistar Kyoto, C-21 dose-dependently increased urine Na+ excretion from 0.023±0.01 to 0.064±0.02, 0.087±0.01, and 0.089±0.01 µmol/min (P=0.008, P<0.0001, and P<0.0001, respectively) and renal interstitial fluid levels of AT2R downstream signaling molecule cGMP (cyclic guanosine 3',5' monophosphate) from 0.91±0.3 to 3.1±1.0, 5.9±1.2 and 5.3±0.5 fmol/mL (P=nonsignificant, P<0.0001, and P<0.0001, respectively). In contrast, C-21 did not increase urine Na+ excretion or renal interstitial cGMP in SHR. Mean arterial pressure was slightly higher in SHR but within the normotensive range and unaffected by C-21. In Wistar Kyoto, but not SHR, C-21 induced AT2R translocation to apical plasma membranes of renal proximal tubule cells, internalization/inactivation of NHE-3 (sodium-hydrogen exchanger-3) and Na+/K+ATPase (sodium-potassium-atpase) and phosphorylation of AT2R-cGMP downstream signaling molecules Src (Src family kinase), ERK (extracellular signal-related kinase), and VASP (vasodilator-stimulated phosphoprotein). To test whether cGMP could bypass the natriuretic defect in SHR, we infused 8-bromo-cGMP. This restored natriuresis, Na+ transporter internalization/inactivation, and Src and VASP phosphorylation, but not apical plasma membrane AT2R recruitment. In contrast, 8-bromo-cAMP administration had no effect on natriuresis or AT2R recruitment in SHR. CONCLUSIONS: The results demonstrate a primary renal proximal tubule cell AT2R natriuretic defect in SHR that may contribute to the development of hypertension. Since the defect is abrogated by exogenous intrarenal cGMP, the renal cGMP pathway may represent a viable target for the treatment of hypertension. Visual Overview: An online visual overview is available for this article.

The Association Between Patterns of Social Engagement and Conversion From Mild Cognitive Impairment to Dementia: Evidence From the Health and Retirement Study.

OBJECTIVES: This study examined the association between patterns of social engagement and conversion from cognitive impairment, no dementia (CIND) to dementia. It also tested whether social engagement is associated with conversion independently from physical and cognitive engagements. METHOD: Data from 2 waves (2010 and 2014) of the Health and Retirement Study (HRS) were used. The sample consisted of 1227 people who had CIND in 2010. To identify the heterogeneity of social engagement, latent class analysis was utilized. Multinomial logistic regression analysis was utilized to investigate the association between patterns of social engagement and probability of conversion to dementia and death or dropout. RESULTS: The result showed that patterns of social engagement that represent higher level and more variety of social engagement were associated with lower probabilities of conversion to dementia in 4 years but not with probabilities of death or dropout. The relationship held after controlling for physical and cognitive engagements. DISCUSSION: Findings implied that promoting social engagement may be protective against developing dementia even for the high-risk group of people with CIND. Future studies should investigate the mechanism behind the relationship between patterns of social engagement and lower probabilities of conversion to dementia.

Challenges and opportunities of age diverse universities: Perspectives from admissions and career services.

Universities are experiencing shifts in age distributions of students, with fewer younger students and an increase in the number of people mid-life and beyond seeking education and job training. Thus, there are strong arguments for universities to embrace opportunities to increase age-diversity on campus. This qualitative study explores the challenges, opportunities, and strategies related to university age-diversity from the perspective of Admissions and Career Services staff from one midwestern university. From focus group data, six subthemes were identified as challenges (fitting in; acclimating; stressors; career concerns; return on investment; and ageism/undervaluing age diversity), three subthemes were identified as assets (intentionality; experienced students; and age diverse educational settings) and eight strategies were recommended to better serve an age-diversity student body (support groups; familial supports; social opportunities; job placement; financial aid; targeted outreach; flexibility in learning; and staff support). This article discusses the benefits and challenges of serving older students from the perspective of staff and administrators and provides action steps for universities to promote age-diversity on campus.

The Impact of COVID-19 on Villages: Results from a National Survey.

Villages are consumer-driven organizations that promote aging-in-place. This study documents the effects of the COVID-19 pandemic on Villages and explores variation in response by age of the organization, size of the membership, staffing model, and geographic location. In summer, 2020, we distributed an online survey to executive administrators of 286 Villages in the network. During the pandemic, over 75% of Villages were seen as more or equally valuable for members. Seventy-seven percent of Villages offered virtual socialization events. Most Villages reported a decrease in service requests, given reductions in need for transportation. New services of food and medication delivery were initiated. There is much variation between organizations, but findings suggest that Villages that are older, have more members, and bigger budgets had more capacity and cushion; and although they took a negative hit in income and participation, it was a smaller hit proportionately, compared to younger and smaller Villages. Villages have demonstrated adaptability and creativity. They kept their operations running, provided services, and offered social connection. Vulnerabilities have been exposed: memberships have dropped for many and some members have not been able to participate as before the pandemic. Many lessons learned can help future developments of the Village model.

Within-couple dissimilarities in functional impairment as determinants of spousal care arrangement among older married couples.

Existing research on spousal care focuses on one spouse receiving care from the other, which fails to address the complexity that is created when both spouses experience some impairments. Our study included situations in which one or both spouses have functional impairments when examining the extent to which spouses from the same couple hold a (dis)similar level of functional impairment and whether such within-couple (dis)similarity has an impact on the spousal care arrangement. A subsample of 1170 older married couples was selected from the 2014 Health and Retirement Study. Descriptive statistics were used for describing the level of each spouse's functional impairment regarding the number of limitations in activities (activities of daily living [ADL]) or instrumental ADL (IADL). Logistic regressions were used to examine whether spousal dissimilarity in functional impairment (dissimilar, similarly low, similarly high) was associated with spousal care arrangement. Within couples with one functionally impaired spouse, the impaired spouse was more likely to receive spousal care when reporting a higher level of ADL/IADL impairment. Within couples with two functionally impaired spouses, the more impaired person was more likely to receive spousal care (without giving back) when spouses reported dissimilar level of IADL impairment; spouses were more likely to report mutual care when they had similarly high levels of IADL impairment. By documenting the role of spousal dissimilarities in functioning for determining spousal care arrangement, our study can inform couple-based interventions that capitalize on each spouse's capabilities and resources.

Research priorities for elder abuse screening and intervention: A Geriatric Emergency Care Applied Research (GEAR) network scoping review and consensus statement.

The Geriatric Emergency Care Applied Research (GEAR) Network (1) conducted a scoping review of the current literature on the identification of and interventions to address elder abuse among patients receiving care in emergency departments and (2) used this review to prioritize research questions for knowledge development. Two questions guided the scoping review: What is the effect of universal emergency department screening compared to targeted screening or usual practice on cases of elder abuse identified, safety outcomes, and health care utilization?; and What is the safety, health, legal, and psychosocial impact of emergency department-based interventions vs. usual care for patients experiencing elder abuse? We searched five article databases. Additional material was located through reference lists of identified publications, PsychInfo, and Google Scholar. The results were discussed in a consensus conference; and stakeholders voted to prioritize research questions. No studies were identified that directly addressed the first question regarding assessment strategies, but four instruments used for elder abuse screening in the emergency department were identified. For the second question, we located six articles on interventions for elder abuse in the emergency department; however, none directly addressed the question of comparative effectiveness. Based on these findings, GEAR participants identified five questions as priorities for future research - two related to screening, two related to intervention, and one encompassed both. In sum, research to identify best practices for elder abuse assessment and intervention in emergency departments is still needed. Although there are practical and ethical challenges, rigorous experimental studies are needed.

Sustaining a Collegewide Teaching Academy as a Community: 10 Years of Experience With the Master Teacher Program at the University of Tennessee College of Veterinary Medicine.

On the basis of strategic initiatives and an evolving focus on educational program enhancement, faculty and staff members designed a structured program to provide leadership and resources for improving instruction and disseminating educational scholarship in a veterinary college. The University of Tennessee College of Veterinary Medicine Master Teacher Program was conceptualized in the teaching academy model as a forum for professional development and dialogue. A small leadership team worked with other faculty to develop the program proposal, including its mission, vision, values, and initial goals. Programming includes monthly meetings to discuss a range of policy, theoretical, and practical topics, as well as periodic workshops focused on current strategic initiatives or hot topics. Ten years later, the program continues to successfully connect educators and have an impact on the college and profession. Attendance has grown steadily; feedback has been positive. Participants rate the program's overall value highly, particularly its impact on their teaching, the opportunity to stay current in educational topics, and the opportunity to learn from colleagues. Discussions within the program have provided valuable input for college policy and practices. Keys to sustained success have included a historical culture emphasizing the teaching mission, alignment with college goals, consistency in leadership and programming, periodic revisions and rebranding, and attention to new faculty and staff needs. This article describes the development, growth, and perceived impact of the program and emphasizes lessons learned and actions taken to sustain its success without additional personnel and at minimal cost.

Recovering from the COVID-19 Pandemic: A Focus on Older Adults.

As we look toward recovery from the COVID-19 pandemic, we overview challenges to be minimized, including economic setbacks, health and well-being effects, and highlighted ageism, racism, and classism. We articulate opportunities to be seized, including increased comfort with technology and online platforms; stronger family and intergenerational connections, renewed energy to combat social isolation; more respect for self-care and time management; increased awareness about the importance of advance directives; and, potentially, increased interest across disciplines to work on issues of aging society. Ongoing efforts to improve policies and programs for longer, healthier lives might now be more productive, as we communicate to consumers, public officials, and everyday citizens who may be more aware of what isn't working, what is at stake, and what might be improved.

Applying Gerontological Social Work Perspectives to the Coronavirus Pandemic.

Social workers are familiar with the challenges brought on by the coronavirus pandemic; and we apply three gerontological social work perspectives that might increase our chances of minimizing negative outcomes and improving health and quality of life for everyone. First, the reality that the older population is very heterogeneous challenges ageism and age-stereotyping that has surfaced with COVID-19. Second, concepts of cumulative disadvantage and intersectionality offer clear explanations of the disparities that are being illuminated and lead us to advocate for fundamental changes to reduce disparities in later life and for people across the life course. Third, a strength-based perspective highlights the assets of the older population and the opportunities for positive developments coming out of the crisis. We can capitalize on momentum to increase advance care planning, to reduce social isolation, and expand the use of on-line technology for service provision. We can bolster our arguments to support older workers, volunteers, and caregivers. The fact that these social work perspectives are so applicable to the coronavirus situation reminds us of their fundamental relevance. Gerontological social work has much to offer in our roles as researchers, educators, practitioners, and advocates during this crisis, and our foundational principles serve us well.

Consolidated Measures of Activity among Older Adults: Results of a Three Data Set Comparison.

This study explores the potential to consolidate a broad range of activity items to create more manageable measures that could be used in statistical modeling of multi-activity engagement. We utilized three datasets in the United States: Panel Study of Income Dynamics, Health and Retirement Study, and Midlife in the United States. After identifying activity items, exploratory and confirmatory factor analysis were used to empirically explore composite activity measures. Findings suggest that discrete activity items can be consolidated into activity domains; however, activity domains differ across datasets depending on availability of activity items. Implications for research and practice are further discussed.

Intrarenal ghrelin receptor inhibition ameliorates angiotensin II-dependent hypertension in rats.

The intrarenal ghrelin receptor (GR) is localized to collecting duct (CD) cells, where it increases epithelial Na+ channel (αENaC)-dependent sodium reabsorption in rodents. We hypothesized that chronic GR inhibition with intrarenal GR siRNA lowers blood pressure (BP) in angiotensin II-dependent hypertension via reductions in αENaC-dependent sodium reabsorption. Uninephrectomized Sprague-Dawley rats ( n = 121) received subcutaneous osmotic pumps for chronic systemic delivery of angiotensin II or vehicle (5% dextrose in water). Rats also received intrarenal infusion of vehicle, GR siRNA, or scrambled (SCR) siRNA. In rats receiving intrarenal vehicle or intrarenal SCR siRNA, systemic angiotensin II infusion increased sodium retention and BP on day 1, and BP remained elevated throughout the 5-day study. These rats also demonstrated increased CD GR expression after 5 days of infusion. However, intrarenal GR siRNA infusion prevented angiotensin II-mediated sodium retention on day 1, induced a continuously negative cumulative sodium balance compared with angiotensin II alone, and reduced BP chronically. Glomerular filtration rate and renal blood flow remained unchanged in GR siRNA-infused rats. Systemic angiotensin II infusion also increased serum aldosterone levels, CD αENaC, and phosphorylated serum and glucocorticoid-inducible kinase 1 expression in rats with intrarenal SCR siRNA; however, these effects were not observed in the presence of intrarenal GR siRNA, despite exposure to the same systemic angiotensin II. These data demonstrate that chronic inhibition of intrarenal GR activity significantly reduces αENaC-dependent sodium retention, resulting in a negative cumulative sodium balance, thereby ameliorating angiotensin II-induced hypertension in rats. Renal GRs represent a novel therapeutic target for the treatment of hypertension and other sodium-retaining states.

AT2 Receptor Activation Prevents Sodium Retention and Reduces Blood Pressure in Angiotensin II-Dependent Hypertension.

RATIONALE: Compound 21 (C-21) is a highly selective nonpeptide angiotensin AT2 receptor (AT2R) agonist. OBJECTIVE: To test the hypothesis that chronic AT2R activation with C-21 induces natriuresis via an action at the renal proximal tubule (RPT) and lowers blood pressure (BP) in experimental angiotensin II (Ang II)-dependent hypertension. METHODS AND RESULTS: In rats, Ang II infusion increased both sodium (Na(+)) retention and BP on day 1, and BP remained elevated throughout the 7-day infusion period. Either intrarenal or systemic administration of C-21 prevented Ang II-mediated Na(+) retention on day 1, induced continuously negative cumulative Na(+) balance compared with Ang II alone, and reduced BP chronically. The effects of C-21 are likely to be mediated by action on the RPT as acute systemic C-21-induced natriuresis was additive to that induced by chlorothiazide and amiloride. At 24 hours of Ang II infusion, AT2R activation with C-21, both intrarenally and systemically, translocated AT2Rs from intracellular sites to the apical plasma membranes of RPT cells without altering the total cellular pool of AT2Rs and internalized/inactivated major RPT Na(+) transporters Na(+)-H(+)-exchanger-3 and Na(+)/K(+)ATPase. C-21 lowered BP to a similar degree whether administered before or subsequent to the establishment of Ang II-dependent hypertension. CONCLUSIONS: Chronic AT2R activation initiates and sustains receptor translocation to RPT apical plasma membranes, internalizes/inactivates Na(+)-H(+)-exchanger-3 and Na(+)/K(+)ATPase, prevents Na(+) retention resulting in negative cumulative Na(+) balance, and lowers BP in experimental Ang II-induced hypertension. Acting uniquely at the RPT, C-21 is a promising candidate for the treatment of hypertension and Na(+)-retaining states in humans.