Biaxial cell stimulation: A mechanical validation.

To analyse mechanotransduction resulting from tensile loading under defined conditions, various devices for in vitro cell stimulation have been developed. This work aimed to determine the strain distribution on the membrane of a commercially available device and its consistency with rising cycle numbers, as well as the amount of strain transferred to adherent cells. The strains and their behaviour within the stimulation device were determined using digital image correlation (DIC). The strain transferred to cells was measured on eGFP-transfected bone marrow-derived cells imaged with a fluorescence microscope. The analysis was performed by determining the coordinates of prominent positions on the cells, calculating vectors between the coordinates and their length changes with increasing applied tensile strain. The stimulation device was found to apply homogeneous (mean of standard deviations approx. 2% of mean strain) and reproducible strains in the central well area. However, on average, only half of the applied strain was transferred to the bone marrow-derived cells. Furthermore, the strain measured within the device increased significantly with an increasing number of cycles while the membrane's Young's modulus decreased, indicating permanent changes in the material during extended use. Thus, strain magnitudes do not match the system readout and results require careful interpretation, especially at high cycle numbers.

A microduplication of the long range SHH limb regulator (ZRS) is associated with triphalangeal thumb-polysyndactyly syndrome.

BACKGROUND: Sonic hedgehog (SHH) plays an important role in defining the anterior-posterior axis in the developing limbs. A highly conserved non-coding sequence about approximately 1 Mb upstream from the sonic hedgehog gene (SHH) was shown to be a long range regulator for SHH expression in the limb bud. Point mutations within this non-coding regulatory region designated ZRS lead to ectopic expression of Shh in the anterior margin of the limb bud, as shown in mice, and cause the human triphalangeal thumb and polysyndactyly (TPT-PS) phenotype. Even though this association is well established, its molecular mechanism remains unclear. METHODS AND RESULTS: We investigated a large pedigree with variable TPT-PS. A single nucleotide exchange within the SHH limb regulator sequence was excluded, but locus specific microsatellite marker analyses confirmed a linkage to this region. Subsequently, array comparative genomic hybridisation (array CGH) was carried out using a submegabase whole human genome tiling path bacterial artificial chromosome (BAC) array revealing a microduplication in 7q36.3 in affected individuals. A duplicated region of 588,819 bp comprising the ZRS was identified by quantitative real-time polymerase chain reaction (qPCR) and direct sequencing. CONCLUSION: A novel microduplication in 7q36.3 results in a similar TPT-PS phenotype as caused by single nucleotide alterations in the ZRS, the limb specific SHH regulatory element. Duplications can be added to the growing list of mechanisms that cause abnormalities of long range transcriptional control.

Site-specific effects of dietary salt intake on guanylin and uroguanylin mRNA expression in rat intestine.

Guanylin and uroguanylin are newly discovered intestinal peptides that have been shown to affect NaCl transport in both the intestine and kidney. The present study tests the hypothesis that guanylin and uroguanylin mRNA expression in each major region of the intestine is regulated by NaCl intake. Semiquantitative multiplex RT-PCR analysis was used to determine the molecular expression of guanylin and uroguanylin in the duodenum, jejunum, ileum, and colon in rats maintained on low (LS), normal (NS), or high (HS) NaCl intake for 4 days. LS intake reduced the expression of uroguanylin, and to a lesser degree, guanylin mRNA in all intestinal segments compared to NS intake. The duodenum was the site of the greatest decrease for both. In contrast, HS intake significantly increased the expression of guanylin mRNA only in the duodenum and jejunum and had minimal effect on uroguanylin mRNA. The minimum time required for altered gene expression was determined by delivering an oral NaCl challenge directly to the gastrointestinal tract by oro-gastric administration to LS or NS animals. In LS rats, NaCl oro-gastric administration significantly increased mRNA expression of both peptides in all intestinal segments. Furthermore, the increases in guanylin and uroguanylin mRNA were detected within 4 h and plateaued by 8 h. Conversely, acute oro-gastric administration of the same NaCl solution to NS rats caused elevations of guanylin mRNA only in the duodenum and jejunum, and of uroguanylin mRNA only in the ileum and colon. In conclusion, the data demonstrate that variations in NaCl intake lead to intestinal segment-specific changes in guanylin and uroguanylin mRNA expression.

Thin section arrays for I-FISH analysis of chromosome-specific imbalances in squamous cell carcinomas of the head and neck.

Thin section arrays of 20 head and neck squamous cell carcinomas were studied by I-FISH for gains (including amplification) and losses of specific genomic segments. These arrays allow the examination not only of a number of tumor sections but also of the surrounding margins and of inconspicuous control tissue in one experiment. All tumor sections examined significantly differed from the inconspicuous control tissues by containing more or less extensive cell populations with aberrant signal constitutions. In no case, however, did the aberrant population constitute the whole area of the section. Gains of signals were strikingly more frequent than were losses. All tumors showed significant gains of the segments examined, the highest differences between tumor and control sections were found for the segments 9q34 and 8q24, followed by 5p15.3 and 11q13. Amplifications were most frequently found of 11q13: 8 of the 20 tumors showed amplifications in more than 20% of the nuclei, while no nucleus with more than four signals was found in any of the control tissues (control: 0%). Amplifications of the target sequences on chromosomes 8 (14 tumors) and 9 (8 tumors) were observed in low but significant percentages of nuclei, no significant cell population was detected with an amplification of 5p15.3. Fourteen tumors exhibited a significant loss of 13q14, and only 8 tumors a significant loss at any other site. In the tumor margin sections, in most cases, the margins apparently were also affected by the one or the other of the genomic changes of the pertinent primary tumor. Nevertheless, there were, in some cases, also large differences depending on the way of analysis, but also on the specific signal constitution considered. Tumor stages T3 and T4 tended to have higher frequency of nuclei with gains of 5p15.3, 8q24, and 11q13 as compared to T2 tumors and less gains of 9q34 and loss of 13q14. With the exception of 8q24 and 13q14 alterations there was also a trend to higher percentages of aberrant nuclei in the margin of T3-4 tumors vs. T2 tumors.

Guanylyl cyclase-C receptor mRNA distribution along the rat nephron.

Guanylin (GN) and uroguanylin (UGN) are two recently identified peptides that have been shown to affect water and electrolyte transport in both the intestine and the kidney. Mechanistically, the effects of both peptides are thought to be mediated by intracellular cGMP which results from ligand binding to a plasma membrane guanylyl cyclase-C (GC-C) receptor. To date, the specific intrarenal site(s) of GN and UGN action have not been established. To begin to address this issue, the present studies utilized semi-quantitative RT-PCR to assess the distribution of GC-C mRNA in specific microdissected segments of the rat nephron. GC-C mRNA expression was highest in the cortical collecting tubule, followed by the proximal convoluted tubule, medullary thick ascending limb and collecting tubule, and thin limbs of Henle's loop. Expression levels were significantly lower in all other segments tested, including the glomerulus. The renal tubular expression pattern for cGMP-dependent protein kinase II (cGK-II) mRNA, which is activated in response to GN/UGN-dependent cGMP accumulation, was similar to that for GC-C. Notably, both GN and UGN mRNAs were also expressed along the nephron. The highest levels of expression for both peptides were detected in the medullary collecting tubule. Lower, but comparable levels of GN and UGN expression also occurred in the cortical collecting tubule, cortical and medullary thick ascending limb, and thin limbs of Henles loop. In the proximal convoluted tubule, GN mRNA expression was also quite high, while UGN mRNA was almost undetectable. The presence of renal GC-C and cGK-II in the kidney are consistent with a proposed endocrine function for GN and UGN. In addition however, the present data suggest that intrarenally synthesized GN and UGN may also contribute to the regulation of renal tubular transport.

Renal effects of uroguanylin and guanylin in vivo.

Uroguanylin and guanylin are newly discovered endogenous heat-stable peptides that bind to and activate a membrane bound guanylyl cyclase signaling receptor (termed guanylyl cyclase C; GC-C). These peptides are not only found in blood but are secreted into the lumen of the intestine and effect a net secretion of electrolytes (Na+, K+, Cl-, HCO3-) and fluid into the intestine via a cyclic guanosine-3', 5'-monophosphate (cGMP) mechanism. GC-C is also the receptor for Escherichia coli heat-stable enterotoxin (STa) and activation by STa results in a diarrheal illness. Employing mouse renal in vivo models, we have demonstrated that uroguanylin, guanylin, and STa elicit natriuretic, kaliuretic, and diuretic effects. These biological responses are time- and dose-dependent. Maximum natriuretic and kaliuretic effects are observed within 30-40 min following infusion with pharmacological doses of the peptides in a sealed-urethra mouse model. Our mouse renal clearance model confirms these results and shows significant natriuresis following a constant infusion of uroguanylin for 30 min, while the glomerular filtration rate, plasma creatinine, urine osmolality, heart rate, and blood pressure remain constant. These data suggest the peptides act through tubular transport mechanisms. Consistent with a tubular mechanism, messenger RNA-differential display PCR of kidney RNA extracted from vehicle- and uroguanylin-treated mice show the message for the Na+/K+ ATPase gamma-subunit is down-regulated. Interestingly, GC-C knockout mice (Gucy2c -/-) also exhibit significant uroguanylin-induced natriuresis and kaliuresis in vivo, suggesting the presence of an alternate receptor signaling mechanism in the kidney. Thus, uroguanylin and guanylin seem to serve as intestinal and renal natriuretic peptide-hormones influencing salt and water transport in the kidney through GC-C dependent and independent pathways. Furthermore, our recent clinical probe study has revealed a 70-fold increase in levels of urinary uroguanylin in patients with congestive heart failure. In conclusion, our studies support the concept that uroguanylin and guanylin are endogenous effector peptides involved in regulating body salt and water homeostasis.

Renal effects of uroguanylin and guanylin in vivo

Uroguanylin and guanylin are newly discovered endogenous heat-stable peptides that bind to and activate a membrane bound guanylyl cyclase signaling receptor (termed guanylyl cyclase C; GC-C). These peptides are not only found in blood but are secreted into the lumen of the intestine and effect a net secretion of electrolytes (Na+, K+, Cl-, HCO3-) and fluid into the intestine via a cyclic guanosine-3',5'-monophosphate (cGMP) mechanism. GC-C is also the receptor for Escherichia coli heat-stable enterotoxin (STa) and activation by STa results in a diarrheal illness. Employing mouse renal in vivo models, we have demonstrated that uroguanylin, guanylin, and STa elicit natriuretic, kaliuretic, and diuretic effects. These biological responses are time- and dose-dependent. Maximum natriuretic and kaliuretic effects are observed within 30-40 min following infusion with pharmacological doses of the peptides in a sealed-urethra mouse model. Our mouse renal clearance model confirms these results and shows significant natriuresis following a constant infusion of uroguanylin for 30 min, while the glomerular filtration rate, plasma creatinine, urine osmolality, heart rate, and blood pressure remain constant. These data suggest the peptides act through tubular transport mechanisms. Consistent with a tubular mechanism, messenger RNA-differential display PCR of kidney RNA extracted from vehicle- and uroguanylin-treated mice show the message for the Na+/K+ ATPase g-subunit is down-regulated. Interestingly, GC-C knockout mice (Gucy2c -/-) also exhibit significant uroguanylin-induced natriuresis and kaliuresis in vivo, suggesting the presence of an alternate receptor signaling mechanism in the kidney. Thus, uroguanylin and guanylin seem to serve as intestinal and renal natriuretic peptide-hormones influencing salt and water transport in the kidney through GC-C dependent and independent pathways. Furthermore, our recent clinical probe study has revealed a 70-fold increase in levels of urinary uroguanylin in patients with congestive heart failure. In conclusion, our studies support the concept that uroguanylin and guanylin are endogenous effector peptides involved in regulating body salt and water homeostasis.

P450 arachidonate metabolites mediate bradykinin-dependent inhibition of NaCl transport in the rat thick ascending limb.

Recent studies from this laboratory demonstrated that bradykinin transiently elevates intracellular Ca2+ and inhibits Cl-reabsorption in the in vitro microperfused medullary thick ascending limb (mTAL) of the rat. The present study was designed to identify the intracellular signaling mechanism(s) that mediate this response. Preincubation with the intracellular calcium chelator BAPTA (10(-5) M) completely eliminated the bradykinin-dependent increase in intracellular Ca2+ and the suppression of Cl- transport. Preincubation with the cGMP-dependent protein kinase inhibitor H-89 (10(-5) M) had no effect on the transport response to bradykinin. In contrast, 17-octadecynoic acid (17-ODYA; 10(-5) M), a suicide-substrate inhibitor of renal cytochrome P450 omega-hydroxylase, completely blocked the transport response to bradykinin, while the cyclooxygenase inhibitor sodium meclofenamate (10(-5) M) had no effect. Finally, addition of the cytochrome P450 omega-hydroxylase metabolite 20-hydroxyeicosatetraenoic acid (20-HETE; 10(-8) M) to the bathing medium significantly inhibited Cl- transport in the mTAL (delta -39 +/- 6.0%; p < 0.05), while the epoxygenase metabolite 5,6-epoxyeicosatrienoic acid (5,6-EET; 10(-8) M) had no effect. These data suggest that the bradykinin-dependent inhibition of Cl- transport in the mTAL of the rat is mediated by cytochrome P450 dependent metabolite(s) of arachidonic acid.

Effects of thoracic volume expansion on cardiorenal function in the conscious rat.

BACKGROUND: Exposure to microgravity results in the loss of fluid and electrolytes. HYPOTHESIS: This study was designed to determine whether loss of fluid and electrolyte by the kidney occur by increased filtration or decreased tubular reabsorption and to investigate the mechanisms involved. METHODS: Vascular and bladder catheters were implanted and the effects of preferential thoracic volume expansion were studied in conscious rats using a new hindlimb supported head-down tilt model designed to simulate the effects of microgravity. Control rats maintained at 0 degree tilt (NT) were compared to rats at 40 degrees head-down tilt (HDT). RESULTS: HDT immediately increased central venous pressure from 1.4 +/- 0.3 to 2.7 +/- 0.3 mm Hg (p < 0.01); which peaked after 8 h. Compared to NT, cumulative sodium excretion significantly increased within 6 h of HDT and remained increased at 24 h (198.8 +/- 40.3 vs. 72.8 +/- 18.4 microEq; p < 0.01). HDT also significantly increased glomerular filtration rate (GFR) at both 6 (p < 0.05) and 24 h (p < 0.01). In contrast, fractional proximal reabsorption (assessed by lithium clearance) was unchanged over the period of HDT, indicating an appropriate proximal tubule response to increased filtered sodium. HDT had no significant effect on plasma catecholamine or atrial natriuretic peptide concentration nor on plasma renin, while plasma aldosterone concentration was increased after 24 h (72.8 +/- 24.0 vs. 32.4 +/- 8.7 ng/dl; p < 0.05); presumably in response to sodium loss during HDT. CONCLUSION: HDT-induced thoracic volume expansion significantly increases sodium excretion, primarily as a result of an increase in GFR.

Acute effects of gentamicin on thick ascending limb function in the rat.

It is well established that the aminoglycoside antibiotics can adversely affect proximal tubule function. Predominantly indirect evidence suggests that aminoglycosides may also affect function of more distal nephron segments. The present study utilized whole kidney clearance, in vivo micropuncture and in vitro microperfusion to directly determine whether acute gentamicin treatment affects sodium chloride transport in the thick ascending limb of the loop of Henle. Gentamicin (25 mg/kg) significantly increased urine flow, as well as sodium, potassium and chloride excretion within 15 min of intravenous injection. Glomerular filtration rate and proximal tubule fluid reabsorption were not altered by acute gentamicin treatment. In contrast, both fractional and absolute loop chloride transport was significantly decreased. In the in vitro microperfused medullary thick ascending limb, luminal but not basolateral administration of gentamicin (1 mM) significantly decreased chloride reabsorption when compared to time controls. These data suggest that the increased urine and electrolyte excretion associated with acute gentamicin treatment is, at least in part, a consequence of decreased transport in the thick ascending limb of Henle's loop.

Hepatitis A outbreak in a neonatal intensive care unit: risk factors for transmission and evidence of prolonged viral excretion among preterm infants.

An outbreak of hepatitis A virus (HAV) infection in a neonatal intensive care unit (NICU) provided the opportunity to examine the duration of HAV excretion in infants and the mechanisms by which HAV epidemics are propagated in NICUs. The outbreak affected 13 NICU infants (20%), 22 NICU nurses (24%), 8 other staff caring for NICU infants, and 4 household contacts; 2 seropositive infants (primary cases) received blood transfusions from a donor with HAV infection. Risk factors for infection among nurses were care for a primary infant-case (relative risk [RR], 3.2), drinking beverages in the unit (odds ratio [OR], infinity), and not wearing gloves when taping an intravenous line (OR, 13.7). Among infants, risk factors were care by a nurse who cared for a primary infant-case during the same shift (RR, 6.1). Serial stool samples from infant-cases were tested for HAV antigen (HAV-Ag) by enzyme immunoassay and HAV RNA by nucleic acid amplification using the polymerase chain reaction. Infant-cases excreted HAV-Ag (n = 2) and HAV RNA (n = 3) 4-5 months after they were identified as being infected. Breaks in infection control procedures and possibly prolonged HAV shedding in infants propagated the epidemic in a critical care setting.

Universal precautions and mortuary practitioners: influence on practices and risk of occupationally acquired infection.

Embalming, the most common funeral practice in the United States, may expose the embalmer to infectious diseases and blood. We surveyed the 860 members of the National Selected Morticians in 1988 to estimate the incidence of self-reported occupational contact with blood and infectious disease, assess morticians' knowledge of acquired immunodeficiency syndrome (AIDS), determine their adherence to universal precautions, and identify predictors of practices designed to reduce risk of occupational exposure to infections. Of 539 (63%) respondents, 212 (39%) reported needle-stick injuries in the past 12 months, and 15 (3%) reported percutaneous exposures to the blood of a decedent with AIDS. Those rating the risk of occupationally acquired human immunodeficiency virus infection as very high or high (194/539 [36%]) were more likely to decline funerals of decedents with antemortem diagnosis of AIDS (59/194 [30%]) and/or to charge more for such funerals (133/194 [69%]) than those who rated the risk as low to moderate (31/345 [9%], 174/135 [51%]).

Angiotensin II does not contribute to rapid reflex control of arterial pressure.

Pharmacological blockade of the renin-angiotensin converting enzyme reportedly alters the heart rate (HR) power spectrum in conscious dogs, suggesting that these hormones contribute to the short-term regulation of arterial blood pressure. We tested this possibility using four independent procedures. First, HR power spectrum was determined in seven awake dogs before and after administration of enalaprilat (300 ng/kg), a converting-enzyme inhibitor. There were no significant changes in the average amplitude for the spectral peak between 0.003 and 0.1 Hz (i.e., the "low-frequency peak"). Second, the HR power spectrum was measured in 11 awake rabbits before and after treatment with deoxycorticosterone acetate (1 mg.kg-1.day-1) and salt (0.9% saline ad libitum) for 7 days to depress plasma renin levels. There were no significant changes in the amplitude of the HR power spectrum, although mean HR decreased from 206 +/- 3 to 184 +/- 4 beats/min after treatment. In the third experiment, another group of rabbits (n = 8) was tested after 2 wk on a low-salt diet to elevate plasma angiotensin levels and then after 2 wk on a normal salt diet. Once again there were no significant effects on the HR power spectrum. Finally, tranquilized dogs (n = 9) were subjected to sinusoidally varying lower body negative pressure at selected frequencies of 0.008-0.12 Hz. Tests were conducted in the control state and after administration of an angiotensin receptor antagonist (saralasin, 1 microgram.kg-1.min-1). Lower body negative pressure-induced fluctuations in arterial blood pressure were similar in both states. We find no evidence for the role of the renin-angiotensin system in the moment-to-moment regulation of arterial pressure and HR.

Calcium, parathyroid hormone, and vitamin D in the "prehypertensive" Dahl salt-sensitive rat.

The purpose of this study was to determine if alterations of calcium and calcium regulating hormones precede the onset of NaCl-induced hypertension in the Dahl salt-sensitive (S) rat. After a 5-day balance study, serum ionized calcium, parathyroid hormone (PTH), and 1,25-dihydroxy vitamin D concentrations were measured in Dahl-S and salt-resistant (R) rats that had been maintained on a "normal" (1%) or high (7%) NaCl intake. Blood pressure was higher in Dahl-S than Dahl-R (P less than .01), but was not affected by 5 days of high NaCl. On both NaCl intakes, urine calcium excretion was increased, serum calcium was decreased, and serum PTH and 1,25 dihydroxy vitamin D were increased in Dahl-S compared to Dahl-R (P less than .01). On the high NaCl intake, fecal calcium was greater in Dahl-S than in Dahl-R, and net 5-day calcium balance was less positive in Dahl-S (P less than .05). Thus, alterations of calcium, PTH, and vitamin D precede NaCl-induced hypertension in Dahl-S. These alterations may contribute to the development of hypertension in this animal model.

Parasympathetic impairment of baroreflex control of heart rate in Dahl S rats.

To test the hypothesis that impaired baroreflex control of heart rate in Dahl salt-sensitive (S) rats is due to an impairment of the parasympathetic limb of the bradycardic response, baroreflex sensitivity was evaluated in conscious, chronically instrumented Dahl S and salt-resistant (R) animals. Sensitivity was impaired in Dahl S rats when bolus doses of phenylephrine were administered (0.863 +/- 0.042 vs. 1.43 +/- 0.055 ms/mmHg), but it was not different than in R rats when tested with sodium nitroprusside. When the sensitivities before and after blocking the parasympathetic nervous system with atropine were compared, it was revealed that 82% of the reflex bradycardia resulting from bolus doses of phenylephrine was due to the parasympathetic nervous system, whereas the majority (73%) of the bradycardia induced by 5-min infusions of phenylephrine was due to withdrawal of sympathetic tone. Neither baroreflex sensitivity to infusions of phenylephrine (73% sympathetic) or to infusions after atropine (100% sympathetic) were significantly different between S and R rats. Therefore, the impairment of the heart rate reflex in Dahl S rats is due to an impairment of the parasympathetic limb of the response. In addition, a high-salt diet before the development of hypertension did not alter baroreflex sensitivity in either Dahl S or R rats.

Effect of Na and Cl infusion on loop function and plasma renin activity in rats.

Inhibition of plasma renin activity (PRA) by saline has been shown to be related to a specific effect of chloride. The purpose of this study was to test the hypothesis that inhibition of renin release by selective chloride infusion in the rat is related to increased chloride transport in the thick ascending limb of the loop of Henle (TALH). Measurements of loop of Henle function were obtained by micropuncture before and after a 5% body wt infusion of solutions containing either 0.15 mol/l NaCl, 0.15 mol/l lysine monohydrochloride (LysCl), or 0.15 mol/l Na-assorted anions (NaAA). Both NaCl and LysCl infusion lowered PRA (60.8 +/- 11.9 to 22.6 +/- 3.7 ng angiotensin I (ANG I).ml-1.h-1 and 53.3 +/- 6.8 to 34.5 +/- 4.6 ng ANG I.ml-1.h-1; P less than 0.05), whereas NaAA infusion had no effect on PRA (66.7 +/- 15.1 to 59.1 +/- 12.4 ng ANG I.ml-1.h-1). Analysis of late proximal and early distal fluid showed that chloride transport in the TALH was significantly elevated by infusion in all three groups, and there were no differences among the groups after infusion. Distal chloride concentration increased in the NaCl and LysCl groups (26 +/- 2 to 37 +/- 1 meq/l and 26 +/- 2 to 36 +/- 2 meq/l; P less than 0.05), but distal chloride concentration decreased in the NaAA group (28 +/- 2 to 22 +/- 1 meq/l; P less than 0.05). There was no correlation between PRA and fluid flow rate or chloride delivery to the distal tubule.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium and calcium regulating hormones in the "prehypertensive" Dahl salt sensitive rat (calcium and salt sensitive hypertension).

The purpose of this study was to determine if alterations of calcium and calcium regulating hormones precede the onset of NaCl induced hypertension in the Dahl salt sensitive (S) rat. After a 5 day balance study, serum ionized calcium, PTH, and 1,25 dihydroxy vitamin D concentrations were measured in Dahl-S and salt resistant (R) rats that had been maintained on a "normal" (1%) or high (7%) NaCl intake. Blood pressure was higher in Dahl-S than R (P less than .01), but was not affected by 5 days of high NaCl. On both NaCl intakes, urine calcium excretion was increased, serum calcium was decreased, and serum PTH and 1,25 dihydroxy vitamin D were increased in Dahl-S compared to Dahl-R (P less than .01). On the high NaCl intake, fecal calcium was greater in Dahl-S than in Dahl-R, and net 5 day calcium balance was less positive in Dahl-S (P less than .05). In contrast to NaCl, a high dietary intake of sodium with anions other than chloride (NaAA) fails to produce hypertension in the Dahl-S rat. NaAA loading resulted in decreased urine calcium excretion (P less than .01), and after 5 days of the high NaAA diet, serum calcium and PTH did not differ in Dahl-S and Dahl-R. Thus, alterations of calcium, PTH, and vitamin D precede NaCl-induced hypertension in Dahl-S. These alterations may contribute to the development of hypertension in this animal model.

Effect of salt deprivation on blood pressure in rats.

In most cases blood pressure (BP) is directly related to NaCl intake. In some studies, BP is increased by low salt intake. The effect of Na and Cl deprivation or selective Na deprivation on BP in the normotensive Sprague-Dawley rat was investigated. In study 1, rats were uninephrectomized and fed low NaCl, normal NaCl, or low Na-normal Cl for 3 wk. BP was higher (P less than 0.05) in rats fed low NaCl and low Na-normal Cl than normal NaCl. Plasma renin activity was stimulated by low NaCl intake but was not different between the other two groups. After captopril treatment, BP was lower in the low NaCl group (73.1 +/- 3.6 mmHg) than in the normal-NaCl (99.2 +/- 6.7 mmHg) or low Na-normal Cl (92.0 +/- 6.7 mmHg) groups. In study 2, intact rats (n = 8 per group) were fed low (less than 0.01%), normal (1%), or high NaCl (4%) for 1 wk. BP and heart rate were higher in the low-NaCl group (P less than 0.05) than in the other two groups. Plasma volumes were not different among the groups. In study 3, two groups of eight rats were given either low NaCl or 2% NaCl for 2 wk. BP (131.4 +/- 3.6 mmHg) and heart rate (402 +/- 11 beats/min) were higher in the low-NaCl group than in the 2% NaCl group (121.1 +/- 3.2 mmHg and 369 +/- 9 beats/min, respectively). In the normotensive Sprague-Dawley rat, low NaCl intake elevated BP when compared with normal or high NaCl intake. Part of the increase in the uninephrectomized, Cl-supplemented group is not dependent on the renin-angiotensin system.

Failure of salt loading to inhibit tissue norepinephrine turnover in prehypertensive Dahl salt-sensitive rats.

To determine if alterations of electrolyte balance or sympathetic nervous system activity are present in Dahl salt-sensitive rats (DS) before the onset of hypertension, we compared electrolyte balances, extracellular fluid volume (inulin space), plasma volume (radiolabeled albumin), and norepinephrine turnover in peripheral tissues (heart and interscapular brown fat) in prehypertensive DS and Dahl salt-resistant rats (DR). Animals were maintained for 5 to 7 days on either a "normal" or high NaCl diet. Tissue norepinephrine turnover was evaluated by measuring the rate at which norepinephrine content decreased following tyrosine hydroxylase inhibition with alpha-methyl-p-tyrosine. Blood pressure was higher (p less than 0.05) in DS (135 +/- 2 [SE] mm Hg) than in DR (129 +/- 2 mm Hg) and was not affected by the diets. Extracellular fluid volume and net Na+ and Cl- balances did not differ between DS and DR. However, plasma volume was greater in DS than in DR (p less than 0.05). In both fat and heart, norepinephrine turnover was decreased by dietary NaCl loading in DR (p less than 0.01), but not in DS. Thus, the tendency of the DS to become hypertensive with high NaCl intake may be related to the combined effects of an increased plasma volume and the failure of high dietary NaCl to inhibit peripheral sympathetic nervous system activity.

Induction, prevention and mechanisms of contrast media-induced acute renal failure.

This study describes the development of an experimental model of reversible acute renal failure following infusion of contrast media radiographic dye. Experiments were also performed to investigate possible methods of prevention as well as examine single nephron mechanisms involved in the pathogenesis of the renal failure. Acute renal failure was consistently produced by indomethacin treatment (18 mg/kg) and an intravenous infusion of contrast media (7 ml/kg) into New Zealand rabbits that had been on a low sodium diet for one week. Glomerular filtration rate (GFR), measured by daily creatinine clearance in unanesthetized animals, was significantly decreased (P less than 0.001) 24, 48, and 72 hours following infusion of the contrast dye. Two weeks after induction of acute renal failure, GFR had returned to control. GFR was unchanged during the same time period when the sodium deprived rabbits were given either indomethacin or contrast media alone. Chronic administration of DOCA (1 mg/kg s.c.) and saline drinking water which increased sodium and solute excretions and decreased plasma renin activity also prevented the decrease in GFR. However, acute infusion of either saline or mannitol, which transiently increased sodium and solute excretions and decreased plasma renin activity, did not protect against the development of acute renal failure. Light microscopy revealed no glomerular or tubular changes and no visible obstruction. Micropuncture experiments were performed on three additional groups of anesthetized rabbits: control, acute renal failure, and recovery. Recovery rabbits were allowed a two week period after renal failure before they were micropunctured.(ABSTRACT TRUNCATED AT 250 WORDS)