Nifedipine induces apoptosis in cultured vascular smooth muscle cells from spontaneously hypertensive rats

Apoptosis (programmed cell death) of smooth muscle cells (SMC) in blood vessels is an essential process involved in the control of vessel wall structure. Several antihypertensive drugs currently used in therapy may exert their pharmacological effects by promoting SMC apoptosis. The biochemical events which regulate SMC apoptosis in the vessel wall are complex, and not well understood. We therefore investigated whether treatment of cultured SMC from normotensive Wistar-Kyoto rats (WKY) and from spontaneously hypertensive rats (SHR) with selected antihypertensive drugs would induce SMC apoptosis. We treated aortic SMC from WKY and SHR in vitro with the L-type Ca2+ channel antagonist, nifedipine; with the nitric oxide donor, sodium nitroprusside (SNAP); with forskolin (an activator of adenylyl cyclase); or with thapsigargin (a selective inhibitor of the sarcoplasmic reticulum (SR), Ca2+-ATPase); and compared their apoptosis-promoting effects in SMC derived from the two strains of rats. SMC were derived from the thoracic aorta of 3-4-week-old WKY and SHR, and were used in passages 7-10. Apoptotic cells were detected by in-situ end labeling using the terminal deoxynucleotide transferase-mediated dUTP-nick end-labeling (TUNEL) method, and by morphological examination. We found that: 1) Treatment of cultured aortic SMC with the L-type Ca2+ channel antagonist, nifedipine (5 X 10(-5) M) for 24 hours induced a significantly higher level of apoptosis in SHR cells than in SMC from WKY. Cells from WKY, following exposure to nifedipine for 72 hours, exhibited a similar response to the cells from SHR treated for 24 hours. This was detectable by both morphological criteria as well as DNA labeling by the TUNEL technique. 2) Similar treatment of these cells with thapsigargin (1 x 10(-7) M) led to morphological alterations characteristic of apoptotic cells in SMC from both WKY and SHR, and cells from SHR but not WKY were labeled by the TUNEL technique at 24 hours. The TUNEL method did however identify cells from both WKY and SHR as apoptotic after 48 and 72 hours of treatment. 3) The addition of SNAP, or forskolin to the cultured SMC induced significant, but low levels of apoptosis in WKY SMC only. This selective apoptosis-promoting effect of nifedipine in SHR SMC may result from differences in the control of intracellular Ca2+ between the two strains of cells, or it may indicate that the signaling pathways which regulate apoptosis are different in SMC from the normotensive and the hypertensive rats. Our findings imply that SMC apoptosis may be a selective target for pharmacological intervention in hypertension.

Vascular beta-adrenoceptor function in hypertension and in ageing

Functional beta-adrenoceptors (beta-AR) have been identified and characterized in blood vessels under in vivo conditions as well as in vascular smooth muscle cells (SMC) grown in culture. Agonist occupancy of beta-AR activates adenylyl cyclase (AC) via the stimulatory guanine nucleotide-binding protein (Gs) and leads to elevations in intracellular adenosine 3'5'-cyclic monophosphate levels (cAMP). Increased cAMP activates the cAMP-dependent protein kinase (PKA), with subsequent phosphorylation of various target proteins. This beta-AR pathway interacts with several other intracellular signalling pathways via cross-talk, so that activation by beta-AR agonists may also modulate other second messengers and protein kinases. SMC beta-AR play an important role in SMC function. In intact blood vessels they mediate SMC relaxation by various intracellular mechanisms, ultimately causing a decrease in intracellular Ca2+ levels. In cultured SMC, activation of the beta-AR pathway results in inhibition of cellular proliferation, the development of SMC polyploidy, and SMC apoptosis. Blood vessels from hypertensive animals are characterized by an increase in SMC cell mass, a greater incidence of SMC polyploidy in the aorta, and an impairment in the beta-agonist-mediated SMC relaxation. Some of these changes may result from an attenuation of beta-AR function due to agonist-induced receptor desensitization caused by the uncoupling of receptors from the Gs-AC system. The phosphorylated beta-AR may in turn trigger new signals and activate different intracellular pathways. However, the details of these mechanisms are still unresolved. Since functional beta-AR play such a prominent and multi-faceted role in SMC function, it is important to understand how these diverse physiological effects are mediated by this receptor system, and how they contribute to the development of hypertension. With ageing, a decrease in beta-AR-Gs-AC coupling is observed, and this is implicated in the reduced responsiveness of SMC. The similarities in SMC beta-AR functional changes in hypertension and in ageing suggest that the underlying mechanisms are also analogous.

Recurrent Pregnancy Loss: Summary and Clinical Recommendations

Recurrent pregnancy loss (RPL) is traditionally defined as three or more consecutive pregnancy losses before 20 weeks of gestation. This problem occurs in approximately 1% of all couples and is a frustrating problem for both the patient and physician. This article provides an overview of the problem, including causes, treatments, and recommendations. Among the numerous proposed causes of RPL, only parental karyotype abnormalities, antiphospholipid syndrome, uterine malformations, and cervical incompetence are universally accepted. There are numerous treatments for RPL, but only the efficacy of heparin and low-dose aspirin in women with antiphospholipid syndrome has been established with properly controlled trials. Even after undertaking a complete evaluation, the cause of RPL remains uncertain in over 50% of cases. These patients should understand that subsequent pregnancies have up to a 70% chance of success without treatment.

Apoptosis in the muscular arteries from young spontaneously hypertensive rats

OBJECTIVE

The purpose of this study was to test the hypothesis that a different incidence of apoptosis occurs in the mesenteric arteries of the spontaneously hypertensive rat (SHR) compared with its normotensive control the Wistar-Kyoto rat (WKY) at 1-2 weeks of age.

DESIGN

We examined the incidence of apoptotic cells in the blood vessel wall of muscular arteries from the SHR and WKY at 1-2 weeks of age using two techniques of apoptosis measurement DNA laddering and 3'-OH end labelling. We also measured the volume of the blood vessel wall components and lumen sizes with the confocal microscope to determine whether a differential incidence of apoptosis occurred between the two rat strains.

METHODS

We used phenol/chloroform extraction to isolate genomic DNA and assess DNA fragmentation, with gel electrophoresis to determine DNA laddering, and 3'-OH end labelling, where the enzyme terminal deoxynucleotidyl transferase catalyses the addition of fluorescein-conjugated nucleotides to the cut ends of DNA, to detect in situ DNA fragmentation. The volume per unit length of the blood vessel structural components was measured by optical sectioning with the confocal microscope.

RESULTS

We found that the SHR had a significantly decreased incidence of cellular apoptosis over WKY. This was true for both the electrophoretic method where SHR had significantly less fragmented DNA (molecular size < 600 bp) than WKY (P= 0.01), and for the microscopic method where SHR had fewer labelled cells in both the adventitia (P= 0.01) and the media (P= 0.0001) layers of large mesenteric arteries. The volumes of the adventitia, media and lumen in the large mesenteric arteries were similar between the two strains at this age.

CONCLUSION

These findings suggest that a differential incidence of cellular apoptosis at the age of 1 -2 weeks may be responsible for the larger media volume found in older SHR and thus contributes to the development of hypertension in these animals.

Anti-beta2-glycoprotein I antibodies in women with recurrent spontaneous abortion, unexplained fetal death, and antiphospholipid syndrome

OBJECTIVE

Studies in rheumatologic and hematologic populations suggest that anti-beta(2)-glycoprotein I antibodies are more specific for the clinical manifestations of antiphospholipid syndrome than anticardiolipin antibodies. However, the association between anti-beta(2)-glycoprotein I and pregnancy loss remains uncertain. We sought to determine whether anti-beta(2)-glycoprotein I is associated with the obstetric features of antiphospholipid syndrome.

STUDY DESIGN

Sera from 4 groups of women were studied: (1) 152 healthy fertile control subjects, (2) 141 subjects with unexplained recurrent spontaneous abortions, (3) 58 subjects with unexplained fetal deaths, and (4) 73 subjects with well-characterized antiphospholipid syndrome. Serum anticardiolipin and anti-beta(2)-glycoprotein I levels were determined by enzyme-linked immunoassay.

RESULTS

Patients with antiphospholipid syndrome had significantly higher levels of immunoglobulin G and immunoglobulin M anticardiolipin and anti-beta(2)-glycoprotein I than the other 3 groups (P <.0001). However, women in the recurrent spontaneous abortion, fetal death, and fertile control groups had similar levels of each antibody. Similarly, there were no differences in the proportion of women with positive test results for each autoantibody in these 3 groups. Linear regression analysis showed significant correlation between anticardiolipin immunoglobulin G and beta(2)-glycoprotein I immunoglobulin G (R (2) = 0.544786, P =.0001) and anticardiolipin immunoglobulin M and beta(2)-glycoprotein I immunoglobulin M (R (2) = 0.525048, P =.0001).

CONCLUSION

Both anticardiolipin and anti-beta(2)-glycoprotein I are associated with antiphospholipid syndrome. However, testing for anti-beta(2)-glycoprotein I does not identify additional patients with either recurrent spontaneous abortions or unexplained fetal deaths who initially have negative test responses for anticardiolipin. This is likely because of the strong correlation between the 2 autoantibodies. Our data do not support routine testing for anti-beta(2)-glycoprotein I in addition to testing for antiphospholipid antibodies in women with recurrent pregnancy loss and unexplained fetal death.

In vitro and in vivo evaluation of a reusable double-channel sphincterotome

BACKGROUND

To date, one reusable, double-channel sphincterotome has been approved by the Food and Drug Administration in the United States. Whether this device can be reprocessed easily and whether it is more durable than currently manufactured disposable sphincterotomes are uncertain.

METHODS

Thirty double-channel, 20 mm, braided-wire sphincterotomes approved for multiple uses were studied in vitro/in vivo with regard to durability and sterilization. A cost analysis of reusable, disposable, and reprocessed disposable sphincterotomes was also carried out.

RESULTS

Three of 10 sphincterotomes evaluated in vitro broke after 3, 4, and 8 uses. Electrical integrity was preserved after 10 uses in the remaining sphincterotomes. Nine sphincterotomes remained functional for at least 3 uses, five for 6 uses, and one for 10 uses. Culture results after inoculation demonstrated contamination with surviving organisms after manual cleaning and no growth after ethylene oxide sterilization. Sixty-one procedures were performed in vivo using 20 sphincterotomes (mean number of uses 3.1). No evidence of procedurally related infection occurred with reuse. Cost per use of this reusable sphincterotome was calculated to be $62.98; it became cost effective after 2.2 and 7.9 uses when compared with disposable and reprocessed, disposable sphincterotomes, respectively.

CONCLUSIONS

This reusable sphincterotome proved to be safe, easily sterilized, and electrically intact after repeated use. In vivo, however, a progressive loss of function limited the mean number of uses to 3.1. In settings that preclude reuse of reprocessed disposable accessories, this reusable sphincterotome may provide a means to decrease costs associated with endoscopic retrograde cholangiopancreatography.

Role of Nr13 in regulation of programmed cell death in the bursa of Fabricius

Apoptotic cell death is developmentally regulated in the chicken bursa of Fabricius. Although apoptosis is low in the embryonic bursa, cell death increases markedly after hatching. The expression of Bcl2 family cell death antagonists was examined to identify the genes that regulate bursal cell apoptosis. The expression of Bcl-xL, A1, and Mcl1 was detected in both embryos and hatched birds, whereas Nr13 was expressed at high levels in embryonic bursa, and decreased significantly after hatching, correlating inversely with apoptosis. The oncogene v-reland phorbol myristate acetate, two known inhibitors of bursal cell apoptosis, induced Nr13 expression. Overexpression of Nr13 in DT40 bursal lymphoma cells protected them from low serum-induced apoptosis. The mechanism of inhibition of apoptosis by Nr13 is likely to involve a critical BH4 domain and interaction with death agonist Bax. Deletion of the BH4 domain converted Nr13 into a death agonist. Bax coimmunoprecipitated with Nr13 and Bax was induced, whereas Nr13 levels diminished when bursal lymphoblasts were induced to apoptosis by dispersion. Bursal transplantation studies demonstrated that Nr13 could prevent the in vivo programmed elimination of bursal stem cells after hatching, suggesting that Nr13 plays a role in maintaining bursal stem cells.

Two-color hybridization assay for simultaneous detection of Bordetella bronchiseptica and toxigenic Pasteurella multocida from swine

Bordetella bronchiseptica and toxigenic Pasteurella multocida are the etiologic agents of swine atrophic rhinitis. Methods currently used for their identification are time-consuming and suffer from a lack of sensitivity. We describe a colony lift-hybridization assay for detection of B. bronchiseptica and toxigenic P. multocida that can be performed with a single colony lift derived from a primary isolation plate without the need for pure subcultures of suspect bacteria. Membranes are hybridized simultaneously to probes derived from the B. bronchiseptica alcA gene and the P. multocida toxA gene. A multicolor development procedure permits sequential detection of bound probes. The assay was tested with 84 primary isolation plates generated from nasal swabs from swine with clinical signs of atrophic rhinitis. Comparison of the results from the colony lift-hybridization assay with those from conventional testing, based on a combination of colony morphology, biochemical reactions, mouse lethality, and enzyme-linked immunosorbent assay, indicated that the colony lift assay has superior sensitivity and comparable specificity. This technique has wide application for diagnostic and experimental studies.

An alternatively spliced form of apobec-1 messenger RNA is overexpressed in human colon cancer

BACKGROUND & AIMS

Apobec-1 is an RNA-specific cytidine deaminase whose forced overexpression in transgenic animals is associated with hepatic carcinogenesis. Apobec-1 messenger RNA (mRNA) undergoes alternative splicing, generating a catalytically inactive peptide, apobec-T. We have examined apobec-1 gene expression in human gastrointestinal tumors and in colon cancer-derived cell lines.

METHODS

Levels of the full-length (apobec-1) and alternatively spliced (apobec-T) mRNAs were measured by RNase protection assay, and apobec-T distribution was determined by immunocytochemical localization.

RESULTS

Apobec-1 mRNA was detectable in normal and colon cancer tissue, metastatic nodules, and certain colon cancer-derived cell lines. Apobec-T mRNA abundance was increased an average of 3.5-fold in colon cancers compared with paired control tissue (range, 0.5-14-fold). Immunocytochemical analysis showed apobec-T expression in normal fetal and adult colon and in gastric and small intestinal adenocarcinomas, colonic tubular adenomas, and both primary and metastatic colonic tumors. Overexpression of apobec-T in a tetracycline-responsive cell line decreased cellular proliferation.

CONCLUSIONS

Apobec-T is expressed in normal, adenomatous, and cancerous gastrointestinal tissues, and levels of the mRNA encoding this peptide are significantly increased in colon cancer. Although its relationship to colon carcinogenesis has not been defined, the regulated overexpression of apobec-T is associated with an altered growth phenotype.

Extramedullary facial plasmacytomas with anaplastic features: a diagnostic dilemma with implications for treatment

Extramedullary plasmacytomas (EMPs) are rare plasma-cell tumors of the soft tissue that occur predominantly in the nasal sinuses and oropharynx. Subcutaneous and cutaneous plasmacytomas of the face are distinctly unusual. The authors report a case of rapidly expanding EMP involving the lip and contralateral nasolabial fold of a native Alaskan man with a 25-year history of recurring solitary bone plasmacytomas (SBP). An incisional biopsy revealed sheets of monotypic plasmablasts with anaplastic features. The pathologic and clinical findings were most consistent with a Richter transformation from a low-grade to a high-grade malignancy, or anaplastic myeloma (AM). With combined chemotherapy and radiation therapy, he achieved a complete response. The clinical and laboratory features of this most unusual plasma-cell dyscrasia are reviewed with an emphasis placed on diagnosis and treatment.

Arterial vasodilation and vascular connective tissue changes in spontaneously hypertensive rats

Arterial hypertrophy in response to hypertension includes increases in the connective tissue proteins elastin and collagen. Regression of arterial hypertrophy depends not only on blood pressure normalization but also on the specific antihypertensive treatment. Consequently, each drug class may exert an influence on connective tissue proteins. We evaluated the arterial connective tissue response of 16-week-old spontaneously hypertensive rats (SHRs) to treatment with minoxidil, 120 mg/L, drinking water for 10 weeks. Despite a decrease in blood pressure, minoxidil had no effect on arterial weight or collagen content but increased elastin content in the abdominal aorta, renal, and superior mesenteric arteries. The increase in elastin content in the abdominal aorta and superior mesenteric artery was accompanied by a decrease in tissue elastase activity. Thus the minoxidil-induced increase in arterial elastin content may be related to a direct effect of the drug to decrease elastase activity in these tissues.

Risk of contamination of sterile biopsy forceps in disinfected endoscopes

BACKGROUND

Previous studies have shown that pathogens may persist within bacterial biofilms in endoscope accessory channels despite high-level disinfection. Breaching the gastrointestinal mucosa with biopsy forceps contaminated at time of passage has the potential to cause cross-infection between patients.

METHODS

We studied contamination risk of sterilized biopsy forceps passed through endoscopes after high-level disinfection. For each trial, five video colonoscopes, duodenoscopes, and gastroscopes were used. All endoscopes had been previously processed and stored for 10 or more hours. Sterile biopsy forceps were inserted and retrieved followed by vortexing the tips in 15 mL of soy broth. Under a laminar flow hood, the broth was filtered through a 0.2 microm millipore membrane and plated. Because of minimal bacterial growth resulting from the above, soy broth (> 20 mL) was flushed through two video colonoscopes, duodenoscopes, and gastroscopes on two occasions and collected. The effluent was plated using a sample of 0.1 mL dilution. The remaining suspension was passed through a millipore filter, and the filter was cultured. All cultures were incubated more than 48 hours.

RESULTS

Biopsy forceps underwent a total of 24 anaerobic and 75 aerobic cultures. Microbacterial growth occurred on 17 plates: 7 from gastroscopes, 5 from colonoscopes, and 5 from duodenoscopes. Fifteen plates grew staphylococcus for a total of 21 colonies, 1 plate grew 1 colony of propionibacter, 2 plates grew diphtheroids for a total of 4 colonies, and 1 plate grew a single colony of lactobacillus. Cultures from soy broth flushed through the various endoscopes grew on 5 plates: 3 from gastroscopes and 2 from duodenoscopes grew a total of 8 colonies of staphylococcus.

CONCLUSIONS

With proper cleaning technique, a 20-minute soak in 2% glutaraldehyde is effective in disinfecting endoscopes. Although current procedures for endoscope disinfection remain imperfect, we found that in this clinical setting, infection of pathogenic gastrointestinal flora is unlikely when using sterile biopsy forceps.

Cross-over study comparing effects of treatment with an angiotensin converting enzyme inhibitor and an angiotensin II type 1 receptor antagonist on cardiovascular changes in hypertension

OBJECTIVE

To compare the blood-pressure-lowering effects of an angiotensin converting enzyme inhibitor, perindopril, with those of an angiotensin II type 1 receptor antagonist, L-158,809, for adult spontaneously hypertensive rats.

DESIGN

A cross-over design was used, to treat adult spontaneously hypertensive rats with one drug for 10 weeks, and then with the other for 5 weeks.

METHODS

Adult, male spontaneously hypertensive rats (aged 15 weeks) were treated daily by gavage for 10 weeks with perindopril (P group) or L-158,809 (L group), then treatment was crossed over so that rats in the P group were treated with L-158,809 (P/L group) and rats in the L group were treated with perindopril (L/P group) for 5 weeks. Blood pressure was measured weekly. Plasma angiotensin converting enzyme activity, renal angiotensin receptor density, and arterial structure and functioning were measured after the single and crossover treatment periods.

RESULTS

Treatment lowered the blood pressure from 206 +/- 2 mmHg in rats in the control group, to 126 +/- 2 in rats in the P group and 150 +/- 2 in rats in the L group. After the cross-over period, blood pressure decreased further from 150 +/- 2 to 129 +/- 3 mmHg in rats in the L/P group, whereas blood pressure of spontaneously hypertensive rats in the P/L group increased from 126 +/- 2 to 148 +/- 2 mmHg. Perindopril treatment almost abolished plasma angiotensin converting enzyme activity, whereas L-158,809 treatment had no effect. Renal angiotensin II receptor density was decreased versus baseline in rats in the P and L groups. The affinity of binding was decreased versus baseline in rats in the L group. A positive correlation to blood pressure was found for mesenteric artery wall thickness and wall: lumen ratio. Concentration for half-maximal effect for the response of mesenteric arteries from rats in the P group to norepinephrine was lower than that of the control group rats. Angiotensin II potentiated the norepinephrine-stimulated contraction of arteries from rats in the control and P groups, but not that of arteries from rats in the groups treated with L-158,809.

CONCLUSION

Perindopril was more effective than was L-158,809 at lowering the blood pressure of adult spontaneously hypertensive rats, and at altering the structure and functioning of the arteries.

Blood pressure and heart rate development in young spontaneously hypertensive rats

The course of hypertension development in young spontaneously hypertensive rats (SHR) was studied by the measurement of changes in systolic blood pressure (BP), body weight, and heart rate (HR) at 2, 3, 4, and 6 wk of age. To achieve this, we compared inbreeding lines of SHR and Wistar-Kyoto rats (WKY) to determine if differences in BP, body weight, or HR were present among inbreeding lines of the same strain or between strains. The effect of these differences on the eventual level of BP was then assessed. We found that BP began to diverge between SHR and WKY at 4 wk of age. Significant differences in systolic BP (24 mmHg) between SHR inbreeding lines at 4 wk of age did not affect the BP at 8 wk (172 vs. 170 mmHg). Pulse pressure was significantly higher in SHR than in WKY at 4 wk of age. HR was elevated in SHR over age-matched WKY at 3 wk of age and positively correlated to the level of BP attained by individual animals at 6 wk (P = 0.037). Moreover, WKY inbreeding lines showing elevated HR developed higher BP (145 vs. 127 mmHg) at 10-12 and 20 wk of age. The prehypertensive tachycardia in SHR was investigated further and found to result from an increased intrinsic HR. Because HR at 3 wk is a genetic trait that can be partitioned into inbreeding lines, and inbreeding lines most expressive of this trait showed the highest eventual BP, we conclude that prehypertensive tachycardia may be an important first step during hypertension development in SHR. Moreover, early elevations in HR are highly predictive (r = 0.41) of hypertension occurrence in the animal population studied.

The effects of dietary sodium on hypertension and stroke development in female stroke-prone spontaneously hypertensive rats

Previous studies on male stroke-prone spontaneously hypertensive rats (SHRSP) have shown that a high-salt diet accelerated the onset of hypertension and stroke, resulting in an increased mortality rate at a younger age. The purpose of this study was to examine whether a similar effect is present in female SHRSP. After weaning at 4 weeks of age, 32 female SHRSP were placed on a Japanese-style rat diet containing either 0.3% NaCl or 4% NaCl. Blood pressure (BP), heart rate, and body weight were measured weekly. Beginning at 9 weeks of age, the SHRSP on the 4% NaCl diet began to show a consistently and significantly higher BP than those in the 0.3% NaCl group, reaching an average BP of 245 +/- 9 mmHg at 16 weeks of age as compared to 184 +/- 3 mmHg in the 0.3% NaCl group. Some female SHRSP in the 4% NaCl group started to exhibit behavioral signs of stroke at 12 weeks of age and 100% mortality was found by 20 weeks. There was 0% mortality in the 0.3% NaCl group at that age. A positive correlation was found between the age at which BP surpassed 220 mmHg and the age death occurred due to stroke. No significant difference was noted in the heart rate or body weight measurements between the two groups. The increased mortality rate in the 4% NaCl diet group was accompanied by organ damage as evidenced by the presence of left ventricular hypertrophy, edematous kidneys, renal malfunction, kidney lesions, and cerebral lesions in these female SHRSP. It is concluded that a high-salt diet exacerbates hypertension and caused an increased mortality rate. This increased mortality rate was associated with an increased left ventricular hypertrophy, kidney damage and subsequent malfunction, and cerebrovascular lesions in these female SHRSP.

Correlation of vascular smooth muscle cell morphology observed by scanning electron microscopy with transmission electron microscopy

Smooth muscle cell (SMC) morphology was studied in rat large mesenteric artery using scanning electron microscopy (SEM), after removal of connective tissue elements with the OsO4/HCl method. Transmission electron microscopy (TEM) was used to correlate the findings of SEM and to assess the effects of digestion on cell ultrastructure. When viewed with SEM, relaxed SMC possessed a smooth, regular surface morphology with longitudinal striations or grooves. TEM examination of cross-sectional profiles of SMC suggested that these striations corresponded to the arrangement of membrane dense bodies within the SMC. The presence of cell contacts among SMC as observed with SEM were confirmed using TEM. Two types of SMC contacts were found: simple appositional contacts and interdigitations. Gap junctions were not observed between SMC in the media. Although structures suggesting nerve networks were observed in the medial-adventitial border with SEM, this could not be confirmed using TEM as a result of alteration in cell ultrastructure with the digestive method. We conclude that the OsO4/HCl method, although useful for SEM, is not suitable for TEM study, because it caused significant alterations of SMC ultrastructure such that organelles and other structures were no longer evident when viewed with TEM.

Prevention of stroke and preservation of the functions of cerebral arteries by treatment with perindopril in stroke-prone spontaneously hypertensive rats

The aim of this study was to determine whether the prevention of stroke with perindopril treatment in stroke-prone spontaneously hypertensive rats (SHRSP) is associated with the preservation of the myogenic properties of the cerebral arteries. After weaning at 4 weeks of age, male SHRSP were fed a Japanese-style rat diet with high salt to induce stroke development. Treatment with perindopril was given by gavage every morning beginning at 6 weeks of age. There were three experimental groups: two groups treated with 4 mg.kg-1.day-1 perindopril for different durations (8 or 12 weeks) and one control group consisting of littermates given distilled water. All the control animals developed stroke and died within 14 weeks of age, and myogenic response of the middle cerebral arteries (MCA) to pressure increase was lost in these animals. In contrast, all the treated SHRSP survived during the treatment period, and myogenic response of the MCA was preserved. After withdrawal of the treatment, SHRSP treated for a longer period (12 weeks) also survived longer than those treated for a shorter period (8 weeks). The subsequent development of stroke and death following treatment withdrawal after 8 or 12 weeks of treatment was associated with the loss of pressure-dependent constriction in MCA. A longer treatment duration also increased the stiffness of the MCA, MCA from SHRSP after 12 weeks of treatment had smaller external and lumen diameters, and thicker walls than those from the 8-week treatment group. In a separate study, we found that treatment of SHRSP with 1 or 4 mg.kg-1.day-1 of perindopril for 24 weeks beginning at 6 weeks of age also protected them against death related to stroke, because these rats survived up to 43 weeks of age, when the experiment was terminated. We conclude that there is an association between the absence of myogenic response in cerebral arteries and stroke development in SHRSP. Perindopril treatment preserves the myogenic response of MCA in SHRSP and prevents the stroke development in these animals. A prolonged treatment could increase the survival of SHRSP through a remodelling of the MCA and increasing the stiffness of the cerebral arteries.

AT1 receptor antagonist treatment caused persistent arterial functional changes in young spontaneously hypertensive rats

The effects of chronic treatment with an AT1 receptor antagonist (L-158,809) on hypertension development and cardiovascular changes were studied in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). L-158,809 treatment (0.6 mg/kg PO) was initiated at 3 weeks of age and lasted 12 weeks, to 15 weeks of age. The treatment prevented hypertension development in the SHR (systolic blood pressure, BP, of 136+/-1 mm Hg compared with 198+/-3 mm Hg in control SHR), and lowered the BP of WKY (99+/-2 vs 128+/-1 mm Hg in control WKY). Treatment significantly reduced the heart weight in SHR and WKY. Ten weeks after treatment withdrawal (25 weeks of age), BP had increased in SHR and WKY to 172+/-8 and 117+/-3 mm Hg, respectively. Body weight and kidney weight were not affected by the treatment. Mesenteric arteries from treated SHR were less responsive than control SHR arteries to periarterial nerve stimulations at transmural pressures higher than 80 mm Hg (15 and 25 weeks). Control WKY arteries were less responsive than control SHR arteries at almost all transmural pressures tested (15 weeks) and to pressures greater than 80 mm Hg (25 weeks). Pretreatment of arteries with 10(-8) mol/L angiotensin II enhanced their response to nerve stimulation in vessels from control SHR and WKY (25 weeks) but not from treatment-withdrawn SHR and WKY. Treatment did not alter arterial reactivity in response to norepinephrine. Alteration in arterial structure due to L-158,809 treatment was found only when measured at a transmural pressure of 100 mm Hg. In conclusion, L-158,809 was effective in preventing hypertension during the treatment period, in reducing hypertension severity during the withdrawal period, and in persistently decreasing the reactivity of the arteries.

Prevention of stroke with perindopril treatment in stroke-prone spontaneously hypertensive rats

OBJECTIVE

To determine the protective effects of perindopril treatment in the prevention of stroke and the relation between preventive effects and the histopathology of the brain and kidneys in male stroke-prone spontaneously hypertensive rats (SHRSP).

DESIGN

Prospective animal study.

INTERVENTIONS

Beginning at 6 weeks of age, SHRSP were treated with either distilled water (control) or perindopril for different periods (8, 12 or 24 weeks) and at different dosages (1 or 4 mg/kg per day).

OUTCOME MEASURES

Regular determination of systolic blood pressure, heart rate and body weight until death; at necropsy, macroscopic and microscopic examinations of the brain and kidneys.

RESULTS

Control SHRSP developed severe hypertension (up to 250 mm Hg) by 11 weeks of age and died of stroke within 14 weeks of age. Treatment with perindopril (4 mg/kg per day for 8 or 12 weeks or either 1 or 4 mg/kg per day for 24 weeks) attenuated the blood pressure rise and prevented stroke. In untreated SHRSP, the last blood pressure measurement before the first stroke sign was significantly higher than in SHRSP of the same age treated with perindopril. Withdrawal of the treatment resulted in a rise in blood pressure in all the treatment groups, to approximately 260 mm Hg within 4 weeks. Most of the rats treated for 8 or 12 weeks died within 10 weeks after withdrawal of treatment, whereas those treated for 24 weeks survived up to 43 weeks of age. Treatment also prevented damage to the brain and kidneys and reduced the severity of lesions in the brain and kidneys after treatment withdrawal.

CONCLUSION

Treatment of SHRSP with perindopril prevents stroke through the suppression of blood pressure rise and prevention of tissue damage in the brain and the kidneys. Longer treatment decreased the rate of mortality due to stroke after the withdrawal of treatment as well as the severity of lesions in the brain and kidneys.

Antihypertensive effects of perindopril treatment in adult spontaneously hypertensive rats

OBJECTIVE

To determine the effect of perindopril treatment and treatment withdrawal in the prevention of hypertension in adult male spontaneously hypertensive rats (SHR).

ANIMALS AND METHODS

Beginning at 15 weeks of age, male SHR were treated with either distilled water (control) or different daily dosages of perindopril (1, 2 or 4 mg/kg) by gavage for 10 weeks, followed by 10 weeks of treatment withdrawal. Systolic blood pressure, heart rate and body weight of adult SHR were determined at regular intervals before, during and after the treatment withdrawal periods. At the end of the treatment withdrawal period, plasma and tissue samples were taken for measurement of noradrenaline levels. Angiotensin-converting enzyme (ACE) activity in the plasma from adult SHR and Wistar-kyoto (WKY) rats treated with perindopril 4 mg/kg for two weeks was measured by a radioassay method 6 and 24 h after treatment.

RESULTS

Treatment with perindopril caused a dose-dependent lowering of blood pressure in SHR during the 10-week treatment. After withdrawal of the treatment, persistent lowering of blood pressure was found in SHR treated with higher dosages (2 or 4 mg/kg), but not in the 1 mg/kg group. There was no difference in the tissue level of noradrenaline among the control group and SHR previously treated with perindopril. In SHR and WKY treated with perindopril for two weeks, plasma level of ACE activity was reduced longer than 24 h compared with their respective controls.

CONCLUSIONS

Chronic treatment of adult SHR with perindopril has a dose-dependent effect on the blood pressure of these animals both during and after withdrawal of treatment, but such a treatment had no long term effects on the noradrenaline levels in various tissues.

Expression of functional beta-adrenoceptors and polyploidy development in cultured vascular smooth muscle cells from spontaneously hypertensive rats

The main objective of this study was to investigate the role of beta-adrenoceptor activation in the development of polyploidy in these cells. Smooth muscle cells (SMCs) were cultured from 3- to 4-, 10- to 12-, and 28- to 30-week-old spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). Functional expression of beta-adrenoceptors was examined by treatment of cultured SMCs with a nonselective beta-adrenoceptor agonist, isoproterenol, or an adenylate cyclase activator, forskolin, or a membrane-permeable analog of adenosine 3',5'-cyclic monophosphate (cAMP), 8-bromo-cAMP, and the measurement of intracellular cAMP levels, using a radioimmunoassay. The effects of these treatments on polyploidy development were also studied by measuring the DNA content of SMCs, using scanning microdensitometry. Treatments with isoproterenol or forskolin increased intracellular cAMP levels in both strains of rats in all three age groups. Addition of the beta-adrenoceptor antagonist DL-propranolol inhibited the isoproterenol-stimulated response in SMCs from both SHR and WKY in all three age groups. The number of polyploid SMCs was significantly increased by treatments with isoproterenol, forskolin, or 8-bromo-cAMP in SMCs from 3- to 4-week-old WKY and SHR, but in the 10- to 12-week age group, an increase was found only in SMCs from WKY. Such treatments had no effect on the incidence of polyploid SMCs in the 28- to 30-week groups. We conclude that (i) beta-adrenoceptors expressed by the SMCs from WKY and SHR at all three ages are functional and are coupled via Gs proteins to the stimulation of adenylate cyclase, (ii) treatments that elevate intracellular cAMP levels (by activation of beta-adrenoceptors or of adenylate cyclase) lead to increased polyploid SMCs from WKY and SHR in the younger age group, confirming a role for the beta-adrenoceptor-adenylate cyclase pathway in the development of polyploidy in cultured SMCs from both of these strains of rats, and (iii) the absence of these treatment effects in the induction of polyploid SMCs in older age groups suggests that in these cells, other factors or processes may be involved in regulating the development of polyploid SMCs.

Structural and functional analysis of small arteries from young spontaneously hypertensive rats

We studied structural and functional changes of small muscular arteries from the mesenteric vascular bed of young spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY) using a new morphometric protocol involving the use of confocal microscopy and a pressurized artery system. At 3 and 4 weeks of age, systolic pressure of SHR and WKY was similar; however, significant structural changes in the mesenteric vasculature were already present in SHR. Arteries fixed under pressure in vitro from SHR had a larger medial volume and increased number of smooth muscle cell layers but similar lumen size compared with arteries from WKY in maximally relaxed conditions. Functional studies showed that SHR arteries contracted more in response to stimulation by KCl and norepinephrine, resulting in a significantly smaller lumen size in these vessels than in those from WKY. SHR arteries precontracted with KCl were also able to maintain a smaller lumen diameter than WKY arteries when challenged with increasing pressure levels. No difference in the sensitivity of response of these arteries to norepinephrine stimulation was found. At 3 and 4 weeks of age, mesenteric arteries from some SHR and WKY were not responsive to periarterial nerve stimulation, and the number of responders was higher in the WKY than SHR. However, a greater degree of contraction was found in SHR arteries responding to field stimulation at 4 weeks than in WKY arteries. We conclude that there is a temporal difference in the rate of functional maturation of the innervation in SHR arteries compared with WKY arteries. Structural changes of the small muscular arteries, caused by an increase in the medial volume, and increased number of smooth muscle cell layers are primary changes that contribute to the development of hypertension in the SHR because these changes are present at the age when blood pressure is similar in SHR and WKY.