Fetal Uninephrectomy Leads to Postnatal Hypertension and Compromised Renal Function

It has been proposed that the number of nephrons an individual has may be inversely related to his or her blood pressure. In this study using female ovine fetuses, nephron number was reduced by performing a fetal uninephrectomy during the period of active nephrogenesis (100 days of gestation, term=150 days). Lambs were born at term and grew at a similar rate. At 5 months of age, ovaries were removed and the carotid artery exteriorized into a fold of skin. Blood pressure and renal function were studied at 6 and 12 months of age. At 6 months of age, uninephrectomized lambs had significantly higher mean arterial blood pressure than sham-operated lambs (89±2 versus 82±2 mm Hg,

Fetal renal and blood pressure responses to steroid infusion after early prenatal treatment with dexamethasone

Maternal infusion of dexamethasone for 48 h early in gestation results in upregulation of mRNA for mineralocorticoid and glucocorticoid (MR and GR) receptors and angiotensin II receptors in ovine fetal kidneys late in gestation. This study sought to determine whether dexamethasone exposure results in changes in renal function and blood pressure responsiveness to infused cortisol or aldosterone in the late-gestation fetus. Merino ewes carrying single fetuses were infused with isotonic saline (Sal; n = 9) or dexamethasone (Dex, 0.48 mg/h; n = 10) for 48 h between days 26 and 28 of gestation (term = 150 days). At 115–122 days, renal function and blood pressure were measured in fetuses during a 4-h infusion of saline, cortisol (100 µg/h), or aldosterone (5 µg/h). Infusions were given in random order at least 2 days apart. Basal blood pressure and renal function were similar in Sal and Dex groups and did not change over the course of saline infusion. Cortisol infusion caused similar increases in blood pressure, urine flow, and glomerular filtration rate (GFR) in the groups. Aldosterone infusion caused a significantly different GFR response between the groups [P(treatment x time) < 0.05], but increase in K excretion and decrease in Na-to-K ratio were similar in the groups. The similar results obtained with cortisol and aldosterone infusion suggest no increased renal functional maturity to those hormones after early prenatal dexamethasone exposure. This suggests that changes in mRNA for MR and GR in kidneys of dexamethasone-exposed fetuses do not result in functional differences and highlights the renin-angiotensin system, as reported previously, as more important in this model

Programming Effects of Short Prenatal Exposure to Dexamethasone in Sheep

Recent studies have linked fetal exposure to a suboptimal intrauterine environment with adult hypertension. The aims of the present study were to see whether prenatal dexamethasone administered intravenously to the ewe between 26 to 28 days of gestation (1) resulted in high blood pressure in male and female offspring and whether hypertension in males was modulated by testosterone status, and (2) altered gene expression for angiotensinogen and angiotensin type 1 (AT1) receptors in the brain in late gestation and in the adult. Basal mean arterial pressure (MAP) at 2 years of age was significantly higher in wethers exposed to prenatal dexamethasone (group D; 106±5 mm Hg, n=9) compared with the control group (group S; 91±3 mm Hg, n=8;

Prenatal glucocorticoid exposure in the sheep alters renal development in utero: Implications for adult renal function and blood pressure control

Moritz KM, De Matteo R, Dodic M, Jefferies AJ, Arena D, Wintour EM, Probyn ME, Bertram JF, Singh RR, Zanini S, Evans RG. Prenatal glucocorticoid exposure in the sheep alters renal development in utero: implications for adult renal function and blood pressure control. Am J Physiol Regul Integr Comp Physiol 301: R500-R509, 2011. First published May 18, 2011; doi:10.1152/ajpregu.00818.2010.-Treatment of the pregnant ewe with glucocorticoids early in pregnancy results in offspring with hypertension. This study examined whether glucocorticoids can reduce nephron formation or alter gene expression for sodium channels in the late gestation fetus. Sodium channel expression was also examined in 2-mo-old lambs, while arterial pressure and renal function was examined in adult female offspring before and during 6 wk of increased dietary salt intake. Pregnant ewes were treated with saline (SAL), dexamethasone (DEX; 0.48 mg/h) or cortisol (CORT; 5 mg/h) over days 26 - 28 of gestation (term = 150 days). At 140 days of gestation, glomerular number in CORT and DEX animals was 40 and 25% less, respectively, compared with SAL controls. Real-time PCR showed greater gene expression for the epithelial sodium channel (alpha-, beta-, gamma-subunits) and Na+-K+ - ATPase (alpha-, beta-, gamma-subunits) in both the DEX and CORT group fetal kidneys compared with the SAL group with some of these changes persisting in 2-mo-old female offspring. In adulthood, sheep treated with dexamethasone or cortisol in utero had elevated arterial pressure and an apparent increase in single nephron glomerular filtration rate, but global renal hemodynamics and excretory function were normal and arterial pressure was not salt sensitive. Our findings show that the nephron-deficit in sheep exposed to glucocorticoids in utero is acquired before birth, so it is a potential cause, rather than a consequence, of their elevated arterial pressure in adulthood. Upregulation of sodium channels in these animals could provide a mechanistic link to sustained increases in arterial pressure in cortisol-and dexamethasone-exposed sheep, since it would be expected to promote salt and water retention during the postnatal period

Effect of early glucocorticoid treatment on MR and GR in late gestation ovine kidney

Effect of early glucocorticoid treatment on MR and GR in late gestation ovine kidney. Background The ontogeny of the renal mineralocorticoid (MR) and glucocorticoid (GR) receptors in the ovine fetus, and the effects of early exposure to synthetic or natural glucocorticoids on the expression of these genes in late gestation were examined. Methods A partial cDNA sequence for the ovine MR was cloned and used to generate primers and probes to measure MR mRNA expression by real-time polymerase chain reaction (PCR). GR mRNA was also measured. Kidneys were collected from ovine fetuses at various stages of gestation (days 60 to 140), twin ovine fetuses at 130 days, from ewes treated at days 26 to 28 with either saline, dexamethasone or cortisol, and adult sheep. Ligand binding was used to determine both GR and MR protein levels in all 130-day-old fetuses and adults. Results No significant changes in the expression of either renal MR or GR were detected throughout gestation. Cytosolic protein levels were higher in the fetal kidneys than in the adult. There was a significant increase in both fetal MR and GR mRNA expression, but not protein levels in kidneys from ewes pretreated with dexamethasone. Conclusions MR and GR mRNA are expressed throughout development in ovine fetal kidneys. Dexamethasone treatment resulted in increased expression of MR and GR mRNA but not protein levels. The dissociation between fetal mRNA and protein levels, relative to adult kidneys, suggests that it may be confounding to draw conclusions based on mRNA levels alone

How do interprofessional student teams interact in a primary care clinic? A qualitative analysis using activity theory

Practice based interprofessional education opportunities are proposed as a mechanism for health professionals to learn teamwork skills and gain an understanding of the roles of others. Primary care is an area of practice that offers a promising option for interprofessional student learning. In this study, we investigated what and how students from differing professions learn together. Our findings inform the design of future interprofessional education initiatives. Using activity theory, we conducted an ethnographic investigation of interprofessional education in primary care. During a 5 months period, we observed 14 clinic sessions involving mixed discipline student teams who interviewed people with chronic disease. Teams were comprised of senior medicine, nursing, occupational therapy, pharmacy and physiotherapy entry level students. Semi-structured interviews were also conducted with seven clinical educators. Data were analysed to ascertain the objectives, tools, rules and division of labour. Two integrated activity systems were identified: (1) student teams gathering information to determine patients' health care needs and (2) patients either as health consumers or student educators. Unwritten rules regarding 'shared contribution', 'patient as key information source' and 'time constraints' were identified. Both the significance of software literacy on team leadership, and a pre-determined structure of enquiry, highlighted the importance of careful consideration of the tools used in interprofessional education, and the way they can influence practice. The systems of practice identified provide evidence of differing priorities and values, and multiple perspectives of how to manage health. The work reinforced the value of the patients' voice in clinical and education processes