Identifying the core concepts of pharmacology education: A global initiative

BACKGROUND AND PURPOSE

In recent decades, a focus on the most critical and fundamental concepts has proven highly advantageous to students and educators in many science disciplines. Pharmacology, unlike microbiology, biochemistry, or physiology, lacks a consensus list of such core concepts.

EXPERIMENTAL APPROACH

We sought to develop a research-based, globally relevant list of core concepts that all students completing a foundational pharmacology course should master. This two-part project consisted of exploratory and refinement phases. The exploratory phase involved empirical data mining of the introductory sections of five key textbooks, in parallel with an online survey of over 200 pharmacology educators from 17 countries across six continents. The refinement phase involved three Delphi rounds involving 24 experts from 15 countries across six continents.

KEY RESULTS

The exploratory phase resulted in a consolidated list of 74 candidate core concepts. In the refinement phase, the expert group produced a consensus list of 25 core concepts of pharmacology.

CONCLUSION AND IMPLICATIONS

This list will allow pharmacology educators everywhere to focus their efforts on the conceptual knowledge perceived to matter most by experts within the discipline. Next steps for this project include defining and unpacking each core concept and developing resources to help pharmacology educators globally teach and assess these concepts within their educational contexts.

Do Medical Students' Learning Styles and Approaches Explain Their Views and Behavior Regarding Lecture Attendance?

INTRODUCTION

Medical students' attendance at lectures, particularly in the preclinical years, has been steadily declining over the years. One of the many explanations offered for this observation is that students have different learning styles and approaches, such that not all of them benefit from attending lectures; however, no studies have specifically examined this possibility. While there is evidence against learning styles as affecting objective measures of learning, they are associated with subjective measures of learning and may therefore influence student behavior. We hypothesized that students' learning styles and/or approaches influence their views about the value and purpose of lectures and their motivation to attend them, which, in turn will affect their behavior.

MATERIALS AND METHODS

A LimeSurvey was distributed to all preclinical students at the American University of Beirut. The survey included questions about demographic data, self-reported attendance rates in Year 1 of medical school, two validated and standardized questionnaires assessing the students' learning styles (visual, auditory, kinesthetic, tactile, group, individual) and learning approaches (superficial, deep, strategic), and a series of questions exploring the students' views about the purpose and value of lectures and their motivation to attend lectures.

RESULTS

No associations were found between learning styles or approaches and attendance rates, but this may have been confounded by the mandatory attendance policy at the time. There were, however, a few positive associations between some learning styles or approaches and the students' views about the value of attending lectures. In particular, students with high scores as auditory learners tended to see absolutely no value in attending lectures, and those with high scores as group, auditory or visual learners, tended to see less value in taking their own notes in lectures. Students with superficial approaches to learning felt that watching videos of a lecture provides equivalent education to attending a lecture. There were no statistically significant associations with either the perceived purpose of lectures or the motivation to attend lectures after correction for multiple testing.

CONCLUSIONS

This study reveals that except for some interesting findings related to auditory learners, differences in learning styles or approaches among students cannot adequately explain differences in their attitudes, and likely, behavior, regarding lecture attendance. The idea that learning styles and approaches can influence educational preferences and outcomes, while attractive and intuitive, continues to require supporting evidence.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40670-021-01362-3.

Pharmacological regulation of cytochrome P450 metabolites of arachidonic acid attenuates cardiac injury in diabetic rats

Diabetic cardiomyopathy (DCM) is a well-established complication of type 1 and type 2 diabetes associated with a high rate of morbidity and mortality. DCM is diagnosed at advanced and irreversible stages. Therefore, it is of utmost need to identify novel mechanistic pathways involved at early stages to prevent or reverse the development of DCM. In vivo experiments were performed on type 1 diabetic rats (T1DM). Functional and structural studies of the heart were executed and correlated with mechanistic assessments exploring the role of cytochromes P450 metabolites, the 20-hydroxyeicosatetraenoic acids (20-HETEs) and epoxyeicosatrienoic acids (EETs), and their crosstalk with other homeostatic signaling molecules. Our data displays that hyperglycemia results in CYP4A upregulation and CYP2C11 downregulation in the left ventricles (LV) of T1DM rats, paralleled by a differential alteration in their metabolites 20-HETEs (increased) and EETs (decreased). These changes are concomitant with reductions in cardiac outputs, LV hypertrophy, fibrosis, and increased activation of cardiac fetal and hypertrophic genes. Besides, pro-fibrotic cytokine TGF-ß overexpression and NADPH (Nox4) dependent-ROS overproduction are also correlated with the observed cardiac functional and structural modifications. Of interest, these observations are attenuated when T1DM rats are treated with 12-(3-adamantan-1-yl-ureido) dodecanoic acid (AUDA), which blocks EETs metabolism, or N-hydroxy-N'-(4-butyl-2-methylphenol)Formamidine (HET0016), which inhibits 20-HETEs formation. Taken together, our findings confer pioneering evidence about a potential interplay between CYP450-derived metabolites and Nox4/TGF-β axis leading to DCM. Pharmacologic interventions targeting the inhibition of 20-HETEs synthesis or the activation of EETs synthesis may offer novel therapeutic approaches to treat DCM.

Factors That Determine the Perceived Effectiveness of Peer Feedback in Collaborative Learning: a Mixed Methods Design

INTRODUCTION

Peer assessment has been promoted as a valuable approach to formative assessment to support learning and peer professionalism. This mixed methods study employed a conceptual framework to explore the factors that enhance the perceived effectiveness of formative peer assessment in the context of team-based learning as a form of collaborative learning.

MATERIALS AND METHODS

The volume and quality of written peer comments of two medical school classes at three time points were analyzed. Focus groups were then conducted to clarify issues that appeared in the quantitative data and to explore other emerging dimensions.

RESULTS

There was a notable deficiency in both the volume and quality of the comments provided, with no improvement over time. Several factors were identified, including some that are logistical and operational and can be corrected easily, such as the timing of the assignments. Others that stood out as major substantive issues and/or limitations related to the students' conceptions of the purpose of the peer assessment and to their interpersonal variables.

DISCUSSION

There were social disincentives for students to provide constructive feedback to peers with whom a continuing working relationship is necessary. There was also an inconsistency between the quality of the peer feedback being typically shallow and lacking in substance, and students considering it beneficial.

CONCLUSION

The findings identify factors that need to be addressed in order to ensure the quality and effectiveness of formative peer assessment among medical students.

Effect of Targeted Curricular Reform on the Learning Environment, Student Empathy, and Hidden Curriculum in a Medical School: A 7-Year Longitudinal Study

OBJECTIVE

The American University of Beirut Faculty of Medicine follows the American model of medical education. In 2013-2014, a carefully designed new curriculum replaced the previous, largely traditional curriculum, and aimed to improve student wellbeing, upgrade the learning environment, enhance student empathy, and counter the negative influences of the hidden curriculum. This longitudinal study assessed the effectiveness of the new curriculum in those domains over a period of 7 years.

METHODS

Three cohorts of medical students anonymously filled a paper-based survey at the end of years 1, 2, 3, and 4 of the 4-year curriculum. These included the Class of 2016, the last batch of students who followed the old curriculum, and 2 cohorts that followed the new curriculum (Class of 2017 and Class of 2019). The perceived learning environment was assessed by the Dundee Ready Education Environment Measurement survey; the student's empathy was assessed by the Jefferson Scale of Physician Empathy-Student version; and the hidden curriculum was examined using a locally developed survey.

RESULTS

The scores on the learning environment survey were significantly higher among the cohorts following the new curriculum relative to those following the old curriculum. Similar significant results appeared when looking at each of the subscales for the learning environment. The students' empathy scores were also significantly higher in both cohorts of the new curriculum when compared with the old curriculum. Nevertheless, there was a significant decrease in empathy in both third and fourth years relative to second year. The new curriculum also improved aspects of the students' perceptions and responses to the hidden curriculum.

CONCLUSION

In conclusion, a well-planned and well-researched curricular intervention, based on sound educational theories, practices, and standards can indeed transform the learning environment, as well as the attitudes, values, and experiences of medical students.

Respecting patient choices: using the 'Go Wish' cards as a teaching tool

BACKGROUND

Individuals have different values and priorities that can have an important impact on their medical management. Understanding this concept can help physicians provide medical care that is in line with the goals of their patients. Communicating this message effectively to students is challenging.

OBJECTIVE

To report our experience with using Go Wish cards in the medical education setting.

DESIGN

A thematic analysis of student reflection papers using grounded theory.

SETTING/SUBJECTS

Second-year medical students participated in an activity using the Go Wish cards as part of a course module on palliative care. The activity aimed to encourage students to reflect on their own choices at the end of life and to highlight that different people have different priorities.

RESULTS

Forty-two students (42%) mentioned the Go Wish activity in their reflections on the module. They reported that the activity demonstrated the different priorities at the end of life, it illustrated the importance of providing personalised care, it promoted self-discovery, it transformed their view of death and dying, and it increased their appreciation of the importance of palliative care.

CONCLUSION

Go Wish cards can be used to help illustrate the variability in priorities of patients. They can be used as an effective to teach medical students about the importance of considering patient preferences when illness progresses.

mTORC2 Signaling Regulates Nox4-Induced Podocyte Depletion in Diabetes

AIM

Podocyte apoptosis is a critical mechanism for excessive loss of urinary albumin that eventuates in kidney fibrosis. Oxidative stress plays a critical role in hyperglycemia-induced glomerular injury. We explored the hypothesis that mammalian target of rapamycin complex 2 (mTORC2) mediates podocyte injury in diabetes.

RESULTS

High glucose (HG)-induced podocyte injury reflected by alterations in the slit diaphragm protein podocin and podocyte depletion/apoptosis. This was paralleled by activation of the Rictor/mTORC2/Akt pathway. HG also increased the levels of Nox4 and NADPH oxidase activity. Inhibition of mTORC2 using small interfering RNA (siRNA)-targeting Rictor in vitro decreased HG-induced Nox1 and Nox4, NADPH oxidase activity, restored podocin levels, and reduced podocyte depletion/apoptosis. Inhibition of mTORC2 had no effect on mammalian target of rapamycin complex 1 (mTORC1) activation, described by our group to be increased in diabetes, suggesting that the mTORC2 activation by HG could mediate podocyte injury independently of mTORC1. In isolated glomeruli of OVE26 mice, there was a similar activation of the Rictor/mTORC2/Akt signaling pathway with increase in Nox4 and NADPH oxidase activity. Inhibition of mTORC2 using antisense oligonucleotides targeting Rictor restored podocin levels, reduced podocyte depletion/apoptosis, and attenuated glomerular injury and albuminuria.

INNOVATION

Our data provide evidence for a novel function of mTORC2 in NADPH oxidase-derived reactive oxygen species generation and podocyte apoptosis that contributes to urinary albumin excretion in type 1 diabetes.

CONCLUSION

mTORC2 and/or NADPH oxidase inhibition may represent a therapeutic modality for diabetic kidney disease. Antioxid. Redox Signal. 25, 703-719.

Interactive and collaborative learning in the classroom at the medical school Automated response systems and team-based learning

There has been a pedagogic shift in higher education from the traditional teacher centered to the student centered approach in teaching, necessitating a change in the role of the teacher from a supplier of information to passive receptive students into a more facilitative role. Active learning activities are based on various learning theories such as self-directed learning, cooperative learning and adult learning. There exist many instructional activities that enhance active and collaborative learning. The aim of this manuscript is to describe two methods of interactive and collaborative learning in the classroom, automated response systems (ARS) and team-based learning (TBL), and to list some of their applications and advantages. The success of these innovative teaching and learning methods at a large scale depends on few elements, probably the most important of which is the support of the higher administration and leadership in addition to the availability of “champions” who are committed to lead the change.

The long-term impact of team-based learning on medical students' team performance scores and on their peer evaluation scores

BACKGROUND

The Faculty of Medicine at the American University of Beirut implemented a new medical curriculum, which included 90 team-based learning (TBL) sessions in years 1 and 2 of medical school.

METHODS

A validated team performance scale (TPS) and peer evaluation of communication skills, professionalism and personal development were collected at different time points during the two years. Grades on the individual and group readiness assurance tests and an evaluation form were collected after every TBL session.

RESULTS

Students generally positively evaluated most TBL sessions as promoters of critical thinking and appreciated the self-learning experience, though they preferred and had better individual grades on those that entailed preparation of didactic lectures. There was a sustained and cumulative improvement in teamwork skills over time. Similar improvement was noted with peer evaluations of communication skills, professionalism, and personal development over time.

CONCLUSIONS

This is the first report about such a longitudinal follow-up of medical students who were exposed to a large number of TBL sessions over two years. The results support the suggestion that TBL improves medical students' team dynamics and their perceived self-learning, problem solving and communication skills, as well as their professionalism and personal development.

Mechanical stretch-induced vascular hypertrophy occurs through modulation of leptin synthesis-mediated ROS formation and GATA-4 nuclear translocation

Background: Obesity and hypertension are associated with increased leptin production contributing to cardiovascular remodeling. Mechanisms involving mechanical stretch-induced leptin production and the cross talk between signaling pathways leading to vascular remodeling have not been fully elucidated.

Methods and Results: Rat portal vein (RPV) organ culture was used to investigate the effect of mechanical stretch on leptin protein expression in vascular smooth muscle cells (VSMCs). Moreover, the involvement of reactive oxygen species (ROS), the RhoA/ROCK pathway, actin cytoskeleton dynamics and the transcriptional factor GATA-4 activation in mechanical stretch-induced vascular remodeling were investigated. Stretching the RPV for 1 or 24 h significantly increased leptin protein level and ROS formation in VSMCs, which was prevented by 1 h pretreatment with the ROCK inhibitor Y-27632 and the actin cytoskeleton depolymerization agent cytochalasin D. Moreover, Western blotting and immunohistochemistry revealed that mechanical stretch or treatment with 3.1 nmol/L leptin for 24 h significantly increased actin polymerization, as reflected by an increase in the F-actin to G-actin ratio. Increases in blood vessels’ wet weight and [³H]-leucine incorporation following a 24 h treatment with conditioned media from cultured stretched RPVs indicated RPV hypertrophy. This effect was prevented by 1 h pretreatment with anti-leptin antibody, indicating leptin’s crucial role in promoting VSMC hypertrophy. As an index of GATA-4 activation, GATA-4 nuclear translocation was assessed by immunohistochemistry method. Pretreating VSMC with leptin for 1 h significantly activated GATA-4 nuclear translocation, which was potently attenuated by the NADPH oxidase inhibitor apocynin, Y-27632, and cytochalasin D.

Conclusion: Our results demonstrate that ROS formation, RhoA/ROCK pathway, and GATA-4 activation play a pivotal role in mechanical stretch-induced leptin synthesis leading to VSMC remodeling.

Temporal cardiac remodeling post-myocardial infarction: dynamics and prognostic implications in personalized medicine

Despite dramatic improvements in short-term mortality rates following myocardial infarction (MI), long-term survival for MI patients who progress to heart failure remains poor. MI occurs when the left ventricle (LV) is deprived of oxygen for a sufficient period of time to induce irreversible necrosis of the myocardium. The LV response to MI involves significant tissue, cellular, and molecular level modifications, as well as substantial hemodynamic changes that feedback negatively to amplify the response. Inflammation to remove necrotic myocytes and fibroblast activation to form a scar are key wound healing responses that are highly variable across individuals. Few biomarkers of early remodeling stages are currently clinically adopted. The discovery of underlying pathophysiological mechanisms and associated novel biomarkers has the potential of improving prognostic capability and therapeutic monitoring. Combining these biomarkers with other prominent ones could constitute a powerful diagnostic and prognostic tool that directly reflects the pathophysiological remodeling of the LV. Understanding temporal remodeling at the tissue, cellular, and molecular level and its link to a well-defined set of biomarkers at early stages post-MI is a prerequisite for improving personalized care and devising more successful therapeutic interventions. Here we summarize the integral mechanisms that occur during early cardiac remodeling in the post-MI setting and highlight the most prominent biomarkers for assessing disease progression.

Blockade of endothelin ET(A), but not thromboxane, receptors offsets the cyclosporine-evoked hypertension and interrelated baroreflex and vascular dysfunctions

The impairment of arterial baroreceptor and vasodilator functions are two major contributors to the hypertensive action of cyclosporine (CSA). In this study, in vivo and in vitro pharmacological studies were performed to investigate whether these effects of CSA are differentially modulated by endothelin and thromboxane signaling. The treatment of rats with CSA (25mg/kg/day i.p.) for 7 consecutive days caused significant increases in blood pressure (BP), attenuated reflex heart rate (HR) responses to vasopressor (phenylephrine, PE) and vasodepressor (sodium nitroprusside, SNP) agents, and reduced cumulative vasorelaxant responses elicited by acetylcholine (Ach, 1×10(-9)-1×10(-5)M) in PE-precontracted isolated aortas. These effects of CSA were blunted after concurrent i.p. administration of atrasentan (selective ETA blocker, 10mg/kg/day), but not terutroban (thromboxane receptor blocker, 10mg/kg/day). Moreover, atrasentan reversed the reductions in aortic protein expression of eNOS caused by CSA whereas terutroban was without effect. We also report that the favorable effect of atrasentan on CSA-evoked impairment in aortic Ach responsiveness disappeared in rats treated simultaneously with L-NAME (NOS inhibitor, 10mg/kg/day) but not BQ 788 (ETB receptor blocker, 0.1mg/kg/day) or indomethacin (cycloxygenase inhibitor, 5mg/kg/day). Together, the data implicate endothelin ETA receptors in baroreflex and vascular derangements which predispose to the hypertensive effect of CSA. Moreover, the facilitation of NOS, but not ETB receptors or cycloxygenase-derived prostanoids, signaling is pivotal for advantageous effect of atrasentan on the aortic CSA-Ach interaction.

Involvement of renal cytochromes P450 and arachidonic acid metabolites in diabetic nephropathy

Diabetic nephropathy (DN) is one of the most serious complications of type I and type II diabetes. DN is characterized by hyperfiltration, hypertrophy, extracellular matrix accumulation, and proteinuria. This advances into renal fibrosis and loss of renal function. Reactive oxygen species (ROS) and TGF-beta have been implicated in the pathogenesis of diabetic nephropathy. Early stages of diabetic nephropathy are also associated with alterations in renal sodium handling as well as hypertension; both are processes linked by involvement of the arachidonic acid (AA) metabolites, 20-hydroxyeicosatetraenoic acid (20-HETE, produced by cytochrome P450-4a, (CYP4A) and epoxyeicosatrienoic acids (EETs). Indeed, metabolism of AA is increased in a rat model of diabetes. In this study, we demonstrate that rats with streptozotocin-induced diabetes of 1 month duration develop renal hypertrophy and increased fibronectin and TGF-beta1 expression/cortical levels concomitant with an increase in CYP4A expression and 20 HETE production. These results were also paralleled by an increase in reactive oxygen species (ROS) production and NADPH oxidase activity. Treatment of diabetic rats with HET0016, selective inhibitor of CYP 4A, prevented all these changes. Our results suggest that diabetes-induced induction of CYP4A and 20-HETE production could be a major pathophysiological mechanism leading to activation of ROS through an NADPH dependent pathway and TGF-beta1 thus resulting in major renal pathology. Inhibitors of 20-HETE production could thus have an important therapeutic potential in the treatment of diabetic nephropathy.

Crowd-funded micro-grants for genomics and "big data": an actionable idea connecting small (artisan) science, infrastructure science, and citizen philanthropy

Biomedical science in the 21(st) century is embedded in, and draws from, a digital commons and "Big Data" created by high-throughput Omics technologies such as genomics. Classic Edisonian metaphors of science and scientists (i.e., "the lone genius" or other narrow definitions of expertise) are ill equipped to harness the vast promises of the 21(st) century digital commons. Moreover, in medicine and life sciences, experts often under-appreciate the important contributions made by citizen scholars and lead users of innovations to design innovative products and co-create new knowledge. We believe there are a large number of users waiting to be mobilized so as to engage with Big Data as citizen scientists-only if some funding were available. Yet many of these scholars may not meet the meta-criteria used to judge expertise, such as a track record in obtaining large research grants or a traditional academic curriculum vitae. This innovation research article describes a novel idea and action framework: micro-grants, each worth $1000, for genomics and Big Data. Though a relatively small amount at first glance, this far exceeds the annual income of the "bottom one billion"-the 1.4 billion people living below the extreme poverty level defined by the World Bank ($1.25/day). We describe two types of micro-grants. Type 1 micro-grants can be awarded through established funding agencies and philanthropies that create micro-granting programs to fund a broad and highly diverse array of small artisan labs and citizen scholars to connect genomics and Big Data with new models of discovery such as open user innovation. Type 2 micro-grants can be funded by existing or new science observatories and citizen think tanks through crowd-funding mechanisms described herein. Type 2 micro-grants would also facilitate global health diplomacy by co-creating crowd-funded micro-granting programs across nation-states in regions facing political and financial instability, while sharing similar disease burdens, therapeutics, and diagnostic needs. We report the creation of ten Type 2 micro-grants for citizen science and artisan labs to be administered by the nonprofit Data-Enabled Life Sciences Alliance International (DELSA Global, Seattle). Our hope is that these micro-grants will spur novel forms of disruptive innovation and genomics translation by artisan scientists and citizen scholars alike. We conclude with a neglected voice from the global health frontlines, the American University of Iraq in Sulaimani, and suggest that many similar global regions are now poised for micro-grant enabled collective innovation to harness the 21(st) century digital commons.

Using team-based learning to teach clinical pharmacology in medical school: student satisfaction and improved performance

Formal teaching in clinical pharmacology was never part of the curriculum at the American University of Beirut Faculty of Medicine. Based on feedback from students and on recommendations of academic bodies, we have introduced, since June 2008, twice-monthly "rational prescribing" sessions during the required internal medicine rotation in year 4 of medical school. All sessions were designed according to the innovative Team-based Learning format and concluded by having the students practice prescription writing and personal formulary development based on the World Health Organization criteria. Our 18-month experience showed that students were very satisfied with the course and the teaching approach, and that their performance on prescription writing and formulary development had improved. Although further studies are needed to explore the impact of team-based learning on additional performance measures, we recommend it as an effective alternative for teaching clinical pharmacology in medical schools.

Pharmacogenetics and personalized medicine: the future for drug prescribing

Pharmacogenetics, the study of interindividual variations in DNA sequence related to drug response, aims at the optimization of treatment regimens based on each patient's unique genetic makeup. Currently, there is a trend towards moving away from the concept of "one drug fits all" to a rather more individualized and personalized medicine. The goal is to define the appropriate drug dose that maximizes efficacy and minimizes toxicity in each individual patient. An example of genotyping for CYP2C9 genetic polymorphisms in patients receiving oral anticoagulants is provided. In spite of its inherent challenges, we hope that pharmacogenetic research and clinical applications expand to improve healthcare outcomes in Lebanon and worldwide.

Using team-based learning to teach pharmacology to second year medical students improves student performance

BACKGROUND

Team-based learning (TBL) is an innovative instructional method that fosters active learning. It has been shown to improve student performance in some health care education courses.

AIM

To examine the effect of teaching pharmacology using a TBL approach on second year medical students' satisfaction and performance.

METHODS

A modified TBL method was used in two case-based discussion sessions of the second year pharmacology course: a relatively easy drug metabolism/pharmacogenetics session and a more challenging pharmacokinetics/pharmacodynamics (PK/PD) session. Individual and group answers to all questions were recorded, and an evaluation form was collected for each session. Class performance on a summative quiz was compared to previous years.

RESULTS

Students provided positive feedback. Group performance was better than individual performance during the TBL exercises. TBL was less successful when the questions were very difficult, with a difficulty range of 30-70% being the most appropriate. Performance of the class on the pharmacology summative quiz showed significant improvement over that in previous years in the PK/PD part, but was unchanged in other topics taught traditionally.

CONCLUSION

The results suggest that TBL provides a better outcome for students, and provide insight into appropriate design of TBL exercises.

PDEs1-5 activity and expression in tissues of cirrhotic rats reveal a role for aortic PDE3 in NO desensitization

Liver cirrhosis is associated with increased nitric oxide (NO) production in the vasculature. We have previously demonstrated that aorta from rats with liver cirrhosis have a reduced relaxant response to NO donors that is corrected by DMPPO, a PDE5-specific inhibitor. Vasodilator responses to DMPPO itself were also reduced in rings from cirrhotic rats. These results supported previous suggestions that upregulation of PDE5 in liver cirrhosis might contribute to renal sodium retention, and consequently modulate vascular reactivity in the context of increased NO production (Tahseldar-Roumieh et al. in Am. J. Physiol. Heart Circ. Physiol. 290, H481-H488, 2006). Here, we investigated the possible alteration in activity and expression of cyclic nucleotide phosphodiesterase PDE1-PDE5 in kidney and vascular tissues in rats 4 weeks after bile duct ligation. The kidney of rats with cirrhosis had increased activity of PDE1 and PDE4 but not PDE5, and increased expression of PDE1A. Unexpectedly and interestingly, there was no change in cirrhotic aorta PDE5, but an increase in PDE3 and PDE4 activity associated with increased expression of PDE3A and PDE3B. Cilostamide, a specific PDE3 inhibitor, corrected the decreased response to an NO donor in isolated aorta from cirrhotic rats, suggesting that the difference in response to NO donors was due to differences in PDE3-induced hydrolysis of cGMP or to cGMP-induced inhibition of PDE3, rather than to differences in PDE5 contribution. In conclusion, these changes in PDE isozymes could greatly contribute to NO desensitization and to the regulation of vascular and renal function in liver cirrhosis.

Temporal changes in vascular reactivity in early diabetes mellitus in rats: role of changes in endothelial factors and in phosphodiesterase activity

The aims of this study were to study the influence of the duration of diabetes, the role of endothelial-derived vasodilators, and the role of phosphodiesterase (PDE) isoform activity in the early changes in vascular reactivity of aortic rings from diabetic rats. Diabetes mellitus was induced in female rats by intravenous streptozotocin (85 mg/kg). Two or 4 wk later, thoracic aortic rings from control and diabetic rats were isolated, and vascular responses to acetylcholine (ACh), S-nitroso-N-acetylpenicillamine (SNAP) [nitric oxide (NO) donor], DMPPO (PDE5 inhibitor), and phenylephrine (PE) were obtained in the presence and absence of endothelium or other drugs. PDE isoform activity was also measured. At 2 wk, responses to ACh and DMPPO were enhanced, whereas those to PE were attenuated in diabetic rats relative to controls. Indomethacin and SQ-29548 (a thromboxane A(2) receptor antagonist), but not N(G)-nitro-L-arginine methyl ester, corrected these differences. The responses to SNAP, and cAMP and cGMP hydrolytic activities, were similar in the two groups. In contrast, at 4 wk, ACh, DMPPO, and PE produced similar responses in the two groups: N(G)-nitro-L-arginine methyl ester rendered the response to PE lower in the diabetic group, and this was corrected by indomethacin, but not SQ-29548, treatment. The response to SNAP was greater in the diabetic group, and this was corrected by DMPPO. Activity of all PDEs was decreased at 4 wk. We conclude that, at 2 wk, there is modulation of thromboxane A(2) production, but no change in the NO system or PDE isoform activities. At 4 wk, a reduction in NO activity is superimposed; at this stage, PDE activity is reduced, together with increased production of vasodilating prostaglandins, possibly as a compensatory mechanism to maintain normal vascular reactivity.

Effect of chronic administration of sildenafil on sodium retention and on the hemodynamic complications associated with liver cirrhosis in the rat

Previous studies demonstrated increased phosphodiesterase-5 (PDE5) activity and expression in the kidneys of rats with liver cirrhosis. Acute intravenous administration of PDE5 inhibitors enhanced sodium excretion in these rats. The aim of the present study was to examine the effects of chronic administration of sildenafil on renal sodium handling and hemodynamics in rats with liver cirrhosis. Male Sprague-Dawley rats underwent bile-duct ligation and excision or sham operation and were housed in metabolic cages throughout the study. Body weight, food intake, water intake and urine volume were measured daily, and plasma samples were obtained twice weekly. Fourteen days following surgery sildenafil or its vehicle (dimethylsulfoxide) were administered (20 mg/kg subcutaneously 3 times/day). Two weeks later, systemic hemodynamics were measured under general anesthesia. Sildenafil enhanced the systemic vasodilatation associated with liver cirrhosis and reduced the arterial pressure. There was no reduction in the glomerular filtration rate, however. Despite these hemodynamic changes, sildenafil prevented the decrease in sodium excretion observed in the bile-duct-ligated group receiving vehicle and markedly increased fractional sodium excretion relative to the other groups. These results suggest that chronic sildenafil administration may help prevent or ameliorate sodium retention in cirrhosis, but that hemodynamic adverse effects may ensue.

Research productivity of the medical faculty at the American University of Beirut

OBJECTIVE

To analyse the quality and quantity of scientific publications of the medical faculty at the American University of Beirut (AUB) during a six year period (1996-2001)

METHODS

The study included all faculty members in the medical school of AUB in the year 2001. A Medline search inclusive of the years 1996-2001 was done for each faculty member and a total number of 881 publications was obtained.

RESULTS

The faculty consisted of 203 members. Their average productivity rate (mean (SD)) was 1.24 (1.38) publications/faculty member/year (PFY), with a mean impact factor of 2.69 (4.63). Eighteen per cent of the faculty did not have any publication in the six year study period, and only 20% had two or more publications per year. There was a significantly higher publication rate among newly recruited faculty members (0.93 (1.40) PFY for those appointed before 1990, 1.45 (1.24) PFY for those appointed during 1990-1995, and 1.67 (1.43) for those appointed after 1995, p = 0.007), and among those who are younger in age (p<0.01). Collaboration with international investigators resulted in more original publications than work done only at AUB (65% v 35%, p<0.001), and a higher journal impact factor for the publications (3.20 (3.85) v 1.71 (2.36), p<0.05).

CONCLUSIONS

This is one of the first studies that analyse the research productivity of the medical faculty in a university setting in a developing country. It shows a wide variation in the research productivity of the faculty members that seems to be related to individual as well as institutional characteristics. Further analysis is needed to define and characterise these factors.

Sesame oil use in ameliorating cough in children: A randomised controlled trial

OBJECTIVES

To examine the role of sesame oil (SO) in reducing the frequency and severity of acute cough in children 2-12 years of age.

DESIGN

Double blind, placebo controlled randomised trial.

SETTING

Seven primary health care centres/clinics in Lebanon. A total of 107 children between the age of 2 and 12 years with cough secondary to common cold were enrolled.

INTERVENTION

Five milliliters of SO or placebo by mouth at bed time.

OUTCOME MEASURES

Cough strength and frequency as judged by parents on a four points Likert scale after giving three syrup doses over three consecutive nights. Analysis was performed on an intention to treat basis.

RESULTS

At day 1, the effect size for cough frequency and cough strength were +0.26 (95%CI -0.64,+0.12) and +0.15 (95%CI -0.53, +0.23), respectively. SO decreased cough symptoms more than placebo but these were not statistically significant. The effect size decreased from days 1 to 3. Cough symptoms improved over the 3 days both in SO and placebo group. No evidence of undesirable effects were noted to SO.

CONCLUSION

Like other over the counter antitussives, SO did not result in marked improvement in cough symptoms.

Alternating ibuprofen and acetaminophen in the treatment of febrile children: a pilot study [ISRCTN30487061]

BACKGROUND

Alternating ibuprofen and acetaminophen for the treatment of febrile children is a prevalent practice among physicians and parents, despite the lack of evidence on effectiveness or safety. This randomized, double-blind and placebo-controlled clinical trial aims at comparing the antipyretic effectiveness and safety of a single administration of alternating ibuprofen and acetaminophen doses to that of ibuprofen mono-therapy in febrile children.

METHODS

Seventy febrile children were randomly allocated to receive either a single oral dose of 10 mg/kg ibuprofen and 15 mg/kg oral acetaminophen after 4 hours, or a similar dose of ibuprofen and placebo at 4 hours. Rectal temperature was measured at baseline, 4, 5, 6, 7 and 8 hours later. Endpoints included proportions of afebrile children at 6, 7 and 8 hours, maximum decline in temperature, time to recurrence of fever, and change in temperature from baseline at each time point. Intent-to-treat analysis was planned with statistical significance set at P < 0.05.

RESULTS

A higher proportion of subjects in the intervention group (83.3%) became afebrile at 6 hours than in the control group (57.6%); P = 0.018. This difference was accentuated at 7 and 8 hours (P < 0.001) with a significantly longer time to recurrence of fever in the intervention group (mean +/- SD of 7.4 +/- 1.3 versus 5.7 +/- 2.2 hours), P < 0.001. Odds ratios (95%CI) for defervescence were 5.6 (1.3; 23.8), 19.5 (3.5; 108.9) and 15.3 (3.4; 68.3) at 6, 7 and 8 hours respectively. Two-way ANOVA with repeated measures over time revealed a significantly larger decline in temperature in the intervention group at times 7 (P = 0.026) and 8 (P = 0.002) hours.

CONCLUSION

A single dose of alternating ibuprofen and acetaminophen appears to be a superior antipyretic regimen than ibuprofen mono-therapy. Further studies are needed to confirm these findings.

Effect of phosphodiesterase 5 inhibitor on alteration in vascular smooth muscle sensitivity and renal function in rats with liver cirrhosis

Previous studies suggested that increased activity of phosphodiesterase (PDE)5 in the kidneys of cirrhotic rats contributes to sodium retention. This study examined the role of PDE5 in the changes in vascular reactivity, hemodynamics, and sodium excretion in rats with liver cirrhosis. Four weeks after bile duct ligation (BDL) or sham operation (SO), in vitro reactivity of aortic rings to various agents and in vivo effects of a PDE5-selective inhibitor [1,3-dimethyl-6-(2-propoxy-5-methanesulfonylamidophenyl)pyrazolo[3,4d]-pyrimidin-4-(5H)-one, DMPPO] were studied. The vasodilator responses to nitroglycerin and S-nitroso-N-acetyl-penicillamine (SNAP) in phenylephrine-precontracted rings without endothelium were attenuated in BDL compared with SO rats. Pretreatment with DMPPO (0.1 microM) enhanced these responses and eliminated the differences between the two groups. Vasodilation to DMPPO itself was also less in BDL rats. The responses to phenylephrine were attenuated in endothelium-rich aorta from BDL relative to SO rats, but they were similar in endothelium-denuded aorta and remained similar despite preincubation with SNAP (0.1 microM) alone or with SNAP and DMPPO. In vivo, BDL rats were vasodilated relative to SO rats; DMPPO (5 mg/kg i.v.) decreased arterial pressure and vascular resistance in both groups equally and caused significant increase in sodium excretion in BDL rats only. In conclusion, the results are in accordance with a possible increase in PDE5 activity in aorta and kidney of cirrhotic rats that results in reduced responses to NO donors and contributes to the increase in sodium retention. PDE5 inhibitors may ameliorate sodium retention in cirrhosis but may worsen vasodilation. Examining the effect of PDE5 inhibitors after chronic administration will be more revealing.

Equal antipyretic effectiveness of oral and rectal acetaminophen: a randomized controlled trial [ISRCTN11886401]

BACKGROUND

The antipyretic effectiveness of rectal versus oral acetaminophen is not well established. This study is designed to compare the antipyretic effectiveness of two rectal acetaminophen doses (15 mg/kg) and (35 mg/kg), to the standard oral dose of 15 mg/kg.

METHODS

This is a randomized, double-dummy, double-blind study of 51 febrile children, receiving one of three regimens of a single acetaminophen dose: 15 mg/kg orally, 15 mg/kg rectally, or 35 mg/kg rectally. Rectal temperature was monitored at baseline and hourly for a total of six hours. The primary outcome of the study, time to maximum antipyresis, and the secondary outcome of time to temperature reduction by at least 1 degrees C were analyzed by one-way ANOVA. Two-way ANOVA with repeated measures over time was used to compare the secondary outcome: change in temperature from baseline at times 1, 2, 3, 4, 5, and 6 hours among the three groups. Intent-to-treat analysis was planned.

RESULTS

No significant differences were found among the three groups in the time to maximum antipyresis (overall mean = 3.6 hours; 95% CI: 3.2-4.0), time to fever reduction by 1 degrees C or the mean hourly temperature from baseline to 6 hours following dose administration. Hypothermia (temperature < 36.5 degrees C) occurred in 11(21.6%) subjects, with the highest proportion being in the rectal high-dose group.

CONCLUSION

Standard (15 mg/kg) oral, (15 mg/kg) rectal, and high-dose (35 mg/kg) rectal acetaminophen have similar antipyretic effectiveness.

Role of humoral mediators in, and influence of a liposomal formulation on, acute amphotericin B nephrotoxicity

The mechanisms responsible for amphotericin B nephrotoxicity remain incompletely understood, but clearly involve reduction in renal blood flow and glomerular filtration rate. Both direct effects of amphotericin B on contractile vascular cells, and indirect effects, due to humoural mediators, have been proposed. This study examines the role of nitric oxide, endothelin and angiotensin II in the acute nephrotoxic effects of amphotericin B in rats, and compares the anti-fungal and nephrotoxic effects of liposomal amphotericin B and amphotericin B-deoxycholate. Anaesthetized rats were given infusions of amphotericin B-deoxycholate in the presence or absence of N-nitro-L-arginine, PD 145065, a non-specific endothelin receptor antagonist, and L-158809, an angiotensin II type I receptor antagonist, or increasing doses of liposomal amphotericin B. Amphotericin B-deoxycholate (0.03 mg/kg/min intravenously) caused a significant 44% reduction in glomerular filtration rate and 65% maximal fall in renal blood flow. N-Nitro-L-arginine-treated rats had a lower renal blood flow and glomerular filtration rate at baseline, but sustained similar reduction of 53% and 75% in these parameters, respectively. PD145065 and L-158809 did not modify these effects either. Increasing doses of liposomal amphotericin B (from 0.01 up to 0.50 mg/kg/min.) induced no change in either glomerular filtration rate or renal blood flow. In vitro susceptibility tests revealed similar potency for liposomal amphotericin B and amphotericin B-deoxycholate in their fungistatic effects and slightly higher potency for amphotericin B-deoxycholate in their fungicidal effect. These results suggest that endogenous endothelin, angiotensin II or nitric oxide systems are not involved in the nephrotoxic effects of amphotericin B. The liposomal amphotericin B results suggest that amphotericin B nephrotoxicity is due to a direct interaction of amphotericin B with renal cells that is prevented by its encapsulation in liposomes.

Influence of phenobarbital on changes in Na(+) handling, hemodynamics and liver function due to partial portal vein ligation in rats

This study examined the influence of phenobarbital, an inducer of hepatic enzymes, on Na(+) handling, hemodynamics and liver function (measured by the rate constant of elimination of aminopyrine in the aminopyrine breath test) after partial portal vein ligation. Rats were randomized to drink either phenobarbital + water or water only for 10 days and then underwent either sham operation or partial portal vein ligation. The aminopyrine rate constant of elimination and Na(+) balance were measured daily before and after surgery; after surgery, hemodynamic measurements were obtained daily in a subset of rats. Phenobarbital raised the baseline aminopyrine rate constant of elimination. Partial portal vein ligation, but not sham operation, caused equivalent reductions in the aminopyrine rate constant of elimination in phenobarbital- and water-treated groups, such that the aminopyrine rate constant of elimination remained higher in the former. Na(+) balance increased significantly in partial portal vein ligation + water, but not sham + water rats on day 1 and then decreased on days 2 and 3. In contrast, neither sham + phenobarbital nor partial portal vein ligation + phenobarbital rats had a significant increase in Na(+) balance. Partial portal vein ligation resulted in vasodilation on day 3 after surgery in the water-treated rats, an effect that was prevented by treatment with phenobarbital. These results support previous suggestions that a reduction in liver function triggers renal Na(+) retention in this model. Vasodilation is not necessary for the latter effect, but also appears to be dependent on a reduction in liver function.

Post-junctional mechanisms involved in the potentiation of cardiac adrenergic responses by cocaine

Cocaine cardiotoxicity is partly due to sympathetic activation of the heart resulting from inhibition of catecholamine uptake at the sympathetic nerve terminal and possible central sympathetic stimulation and/or inhibition. This study evaluated the role of postsynaptic mechanisms in potentiation by cocaine of cardiac adrenergic responses. Cardiovascular responses (arterial and left ventricular pressure, contractility and heart rate) to increasing doses of noradrenaline and to isoproterenol were obtained in anesthetized cats during a control period, after irreversible alpha-adrenoceptor blockade with phenoxybenzamine (5 mg/kg i.v.), and after cocaine (5 mg/kg, i.v.). Responses to noradrenaline were significantly reduced by phenoxybenzamine with lowering of the maximal rise of all parameters. Cocaine shifted the dose-response curve of noradrenaline to the left and enhanced its maximal effects. Some responses to isoproterenol, which is not taken up by nerve terminals, were also enhanced by cocaine. Pretreatment with chlorisondamine or verapamil prevented the cocaine-induced enhancement of the maximal response to noradrenaline and the response to isoproterenol, but it did not inhibit potentiation of submaximal doses. Lidocaine did not potentiate the response to noradrenaline or isoproterenol. Use of chlorisondamine instead of cocaine potentiated responses to all noradrenaline doses and enhanced the responses to isoproterenol. These results suggest that the potentiation by cocaine of cardiac responses to adrenergic stimuli involves presynaptic mechanisms to block noradrenaline re-uptake, and postsynaptic mechanisms to raise the maximal responses. The latter may result from inhibition of central sympathetic outflow or from activation of cardiac Ca(+) channels, leading to increased cardiac sensitivity to noradrenaline.

In-hospital mortality after acute myocardial infarction in Lebanon: incidence, associations, and influence of newer treatment regimens

PURPOSE

To study the incidence of in-hospital mortality following acute myocardial infarction in Lebanon, and its relationship to demographic, clinical variables, and therapeutic strategies.

PATIENTS & METHODS

Consecutive admissions due to myocardial infarction to 18 medical centers in various regions of Lebanon were entered into the Lebanese Myocardial Infarction Study, conducted between January and July 1996. Information was obtained on age, gender, time of onset of symptoms, delay to hospital arrival, mode of transport, and coronary risk factor analysis. The patients were followed up in hospital for analysis of modes of therapy, complications and mortality.

RESULTS

There were 44 in-hospital deaths among the 433 admissions (10.2%), which is a rate lower than those previously reported from Lebanon. Less than half the patients presented within 6 hours of onset of symptoms and only 28% received thrombolytic therapy. The mortality rate was higher in older age groups, those presenting with cardiogenic shock or pulmonary edema, those with a history of angina, infarction or heart failure, and those who developed recurrent ischemia or infarction during their hospital stay. Furthermore, occurrence of ventricular arrhythmias, mechanical complications, congestive heart failure and left bundle branch block was associated with a higher mortality rate. Treatment with angiotensin converting enzyme inhibitors, beta-blockers, aspirin, heparin, nitrates and thrombolytics significantly reduced mortality rates.

CONCLUSIONS

The results reveal improvement in the survival of patients after acute myocardial infarction to values similar to those reported from Western countries. Further effort should be expended to enhance early arrival to the hospital, increased thrombolytic therapy and to implement treatment strategies supported by large clinical trials such as use of aspirin, ACE inhibitors and beta-blockers.

Drug-related hospitalization at a tertiary teaching center in Lebanon: incidence, associations, and relation to self-medicating behavior

OBJECTIVE

In Lebanon there is very limited restriction on drug use. Accordingly, self-medication is highly prevalent. This study examined the influence of these factors on the development of drug-related illnesses that lead to hospitalization.

METHODS

Patients admitted to the medical and pediatric wards of a tertiary teaching center in Beirut, Lebanon, over a period of 6 months were interviewed and their charts were reviewed. Admissions attributable to adverse drug reactions or therapeutic failures were identified and characterized with respect to demographic factors, medical history, drug intake, and self-medicating behavior. The influence of these variables on the development of drug-related illnesses was examined by logistic regression.

RESULTS

Of 1745 adults and 457 children, there were 177 (10.2%) and 36 (7.9%) drug-related illnesses, respectively. Adverse drug reactions accounted for 7.0% and 5.7% and therapeutic failures for 3.2% and 2.2% of adult and pediatric admissions, respectively. Self-medication was commonly practiced (52.6% of adults and 41.6% of children). Logistic regression analysis revealed that female sex increased the risk of adverse drug reaction in adults, whereas self-medication decreased the risk. In children, the risk of adverse drug reaction was increased in lower socioeconomic groups, whereas the risk of therapeutic failure was increased by a positive history of atopy or drug reaction.

CONCLUSIONS

These results provide the first detailed analysis of the problem of drug-related illnesses in a developing country and identify a number of related or risk factors. Despite the lack of regulation of drug dispensing and the unchecked access to drugs in Lebanon, the incidence of drug-related illnesses is not different from that in Western nations. This finding may have relevance to policies of drug regulation in other countries.

Reduced liver function is the trigger for renal sodium retention following portal vein ligation in the rat

Sodium retention along with peripheral vasodilation are features of prehepatic portal hypertension. In several models of experimental liver damage, sodium retention occurs only when hepatic function, measured by the aminopyrine breath test (ABT-k), falls below a critical threshold. The relationship between renal sodium handling, ABT-k and systemic and renal haemodynamics in partial portal vein ligated (PVL) rats was examined to test hypothesis that peripheral vasodilation was responsible for initiating sodium retention. Haemodynamic measurements were conducted early after surgery in portal hypertensive rats with and without sodium retention and in sham-operated controls. Compared with control, both PVL groups of rats had elevated portal pressure and lower peripheral vascular resistance (P < 0.05). Sodium retaining-PVL rats had both lower ABT-k (0.95 +/- 0.05 vs 1.38 +/- 0.06 x 10(-2)/min; P < 0.05) and higher sodium balance (1.38 +/- 0.09 vs 0.43 +/- 0.09 mmol/day; P < 0.05) than non-sodium retaining PVL rats. No differences in plasma renin activity or noradrenaline concentrations were observed. In a separate group of rats, hydralazine-induced pheripheral vasodilation did not induce sodium retention. These results suggest that the presence of peripheral vasodilation alone is not sufficient to trigger a sodium-retaining status. A factor, probably liver function-dependent, acting directly on renal tubules may be necessary for changes in renal sodium handling in this model.

Adenosine does not mediate renal sodium retention and peripheral vasodilation elicited by partial portal vein ligation in rats

This study was conducted to assess the role of adenosine in the peripheral vasodilation and sodium retention that occurs after partial portal vein ligation (PVL) in the rat. The experiment was performed on day 1 after surgery when transient maximal sodium retention developed and day 7 when rats returned to sodium balance. Hemodynamic studies were conducted under anesthesia in portal hypertensive rats with sodium retention and in sham-operated controls. Measurements were obtained before and after administration of a nonselective A1 and A2 adenosine receptor antagonist 1,3-dipropyl-8-p-sulfophenylxanthine (DPSPX) (10 mg/kg intravenously followed by 150 micrograms/min). Under baseline conditions, portal hypertensive rats with sodium retention were hypotensive, with decreases in total peripheral resistance and filtration fraction on day 1 in comparison with the control group. Although hyperdynamic circulation was still maintained by day 7, there was a return to sodium balance. The adenosine receptor antagonist had a modest vasoconstrictor effect on systemic and renal vasculature in both groups, but less in portal hypertensive rats. However, no change in glomerular filtration rate was observed. DPSPX induced a natriuresis in control rats (from 0.40 +/- 0.11 to 5.97 +/- 0.61 mEq/min on day 1, from 0.48 +/- 0.20 to 6.34 +/- 0.45 mEq/min on day 7). This response was attenuated in portal hypertensive rats on day 1 (from 0.14 +/- 0.04 to 1.67 +/- 0.57 mEq/min). but not on day 7 (from 0.20 +/- 0.06 to 5.11 +/- 0.55 mEq/min). These results suggest that in portal hypertensive rats (1) adenosine is not responsible for vasodilation and sodium retention, (2) a sodium-retaining factor acting directly on the renal tubule is responsible for sodium retention.

Nitric oxide does not contribute to sodium retention and peripheral vasodilation induced by partial portal vein ligation in rats

The role of nitric oxide (NO) synthesis in the peripheral vasodilation and sodium retention that occurs after partial portal vein ligation (PVL) was investigated. Hemodynamic studies in PVL rats with sodium retention and in sham-operated controls were conducted on the day when PVL rats developed transient and maximal sodium retention. Measurements were obtained before and during two consecutive periods after NO synthesis inhibition with NG-monomethyl-L-arginine (L-NMMA). Under baseline conditions, PVL rats with sodium retention were hypotensive, with equivalent decreases in total peripheral resistance and glomerular filtration rate in comparison to the control group. After L-NMMA, peripheral resistance and arterial pressure increased by similar extent in both groups. As compared with controls, PVL rats with sodium retention remained hypotensive and vasodilated. Furthermore, L-NMMA-induced natriuresis was attenuated in the PVL group. Additionally, serum and urinary levels of nitrate and nitrite did not vary before surgery and at the time of sodium retention. These results suggest that in PVL rats (1) vasodilation is not NO mediated; (2) vasodilation is not a sufficient explanation for sodium retention, and (3) a sodium-retaining factor acting on the renal tubules is responsible for sodium retention.

Potassium depletion potentiates amphotericin-B-induced toxicity to renal tubules

Hypokalemia and potassium depletion are frequent complications of amphotericin B therapy. Both ischemic and gentamicin-induced renal failure is potentiated by potassium depletion; it is, therefore, possible that amphotericin B nephrotoxicity is similarly influenced. This study evaluated whether the acute nephrotoxic response to amphotericin B is potassium sensitive. Potassium-depleted and control rats were subjected to an acute intravenous infusion of either amphotericin B (AmB-K; AmB, n = 10 in each) or its vehicle (V-K, V; n = 6 in each). Potassium-depleted rats had both lower urinary daily excretion and lower plasma levels of potassium than control animals (0.1 +/- 0.0 vs. 2.1 +/- 0.2 mEq/day, p < 0.001, and 3.8 +/- 0.2 vs. 1.9 +/- 0.1 mEq/l, p < 0.001, respectively). In AmB and AmB-K groups, there were equivalent falls in glomerular filtration rate and renal blood flow, and a rise in renal vascular resistance, compared with V and V-K. In contrast, the AmB-K group showed a higher urinary excretion of sodium (AmB-K vs. AmB: 2.9 +/- 0.7 vs. 1.1 +/- 0.3 microEq/min; p < 0.05) and fractional excretion of Na (AmB-K vs. AmB: 1.6 +/- 0.4 vs. 0.6 +/- 0.1%; p < 0.05) in comparison to the AmB group. Neither of these parameters changed in either amphotericin B or vehicle-treated groups. These results suggest that potassium depletion does not influence the acute renovascular effects of amphotericin B but potentiates its tubular toxicity. This may have clinical implications since hypokalemia and potassium depletion are frequent complications of amphotericin B therapy.

Relationship between oxidative hepatic metabolism, urinary sodium excretion and sympathetic nerve activity in experimental cirrhosis in the rat

This study investigated the relationship between changes in renal sympathetic activity as assessed by renal norepinephrine spill-over and the onset of renal sodium retention in the phenobarbital/carbon tetrachloride model of experimental cirrhosis in rats. In this model, sodium retention occurs when hepatic function, assessed by the aminopyrine breath test (ABT), falls below a critical threshold. Three groups of rats, studied on a constant salt diet, included a group with cirrhosis and sodium retention, a group with cirrhosis of similar duration and no sodium retention and a time-control phenobarbitaltreated group. ABT, renal plasma flow (RPF), glomerular filtration rate (GFR) and mean arterial pressure (MAP) were measured at the time of catecholamine sampling in anesthetized rats. Cirrhosis was associated with reductions in MAP, no change in RPF and GFR, and an ABT below the threshold in rats with sodium retention. In contrast, rats without sodium retention had liver function above the threshold. Renal norepinephrine spill-over increased continuously from controls to non-sodium retaining and sodium retaining animals. The difference between sodium retaining animals and controls was significant. Norepinephrine spill-over correlated to ABT and MAP but not urinary salt excretion. The data suggest that, under these experimental conditions, increased sympathetic activity may contribute to the onset of sodium retention. A plausible explanation for the continuous increase is that catecholamines are released as a compensatory mechanism in response to a primary yet undefined vasodilator.