Ligands of the peripheral benzodiazepine receptor induce apoptosis and cell cycle arrest in oesophageal cancer cells: involvement of the p38MAPK signalling pathway.

Specific ligands of the peripheral benzodiazepine receptor (PBR) are known to induce apoptosis and cell cycle arrest in oesophageal cancer cells. However, the underlying mechanisms are still unknown. Here, we investigated the transcriptional alterations and activation of protein kinases in response to PBR-specific ligands. Using cDNA arrays, we examined the transcriptional effects of the PBR-specific ligand FGIN-1-27 in two oesophageal cancer cell lines, KYSE-140 (squamous cell carcinoma) and OE-33 (adenocarcinoma). In oesophageal cancer cells, FGIN-1-27 induced extensive changes in the expression of genes involved in the regulation of apoptosis and cell cycle. Both in oesophageal cancer cell lines (KYSE-140, OE-33) we observed a strong upregulation of the growth arrest and DNA-damage-inducible genes, gadd45 and gadd153, in response to PBR ligands. gadd genes are known to be induced by p38MAPK activation. Using Western blotting we detected a time- and dose-dependent phosphorylation of p38MAPK, which was found to be functionally involved in gadd induction, apoptosis, and cell cycle arrest. In conclusion, our data indicate that PBR-specific ligands cause apoptosis and cell cycle arrest by activation of the p38MAPK pathway and induction of gadd45 and gadd153.

Oesophageal squamous cell neoplasia in head and neck cancer patients: upregulation of COX-2 during carcinogenesis.

Patients with (previous) head and neck cancer (HNC) are at high risk for developing second squamous cell cancer of the oesophagus. The role of cyclooxygenase-2 (COX-2) in oesophageal squamous carcinogenesis has not yet been investigated in this high-risk group. Therefore, this study examined COX-2 mRNA and protein expression in oesophageal biopsies and resected tissues of 44 HNC patients. The evaluation covered 55 oesophageal tissue samples (18 invasive oesophageal squamous cell cancers, four high- and eight low-grade dysplasias, 25 normal squamous epithelia) from the 44 patients. mRNA levels of COX-2 were measured by real-time PCR using a LightCycler. COX-2 protein expression was studied immunohistochemically and graded by a staining score. COX-2 mRNA was detected in all samples, and its levels correlated positively with the immunohistochemical staining score (P<0.05). COX-2 expression was upregulated during oesophageal squamous carcinogenesis in HNC patients, that is COX-2 expression increased significantly from normal oesophageal squamous epithelium to low- and high-grade dysplasia and finally to invasive squamous cell cancer (P<0.001). Our findings suggest that COX-2 upregulation contributes to oesophageal squamous carcinogenesis in HNC patients. Prospective studies are needed to evaluate the chemopreventive potential of COX-2 inhibitors in this high-risk group.

Extracellular nucleotides inhibit growth of human oesophageal cancer cells via P2Y(2)-receptors.

Extracellular ATP is known to inhibit growth of various tumours by activating specific purinergic receptors (P2-receptors). Since the therapy of advanced oesophageal cancer is unsatisfying, new therapeutic approaches are mandatory. Here, we investigated the functional expression and potential antiproliferative effects of P2-purinergic receptors in human oesophageal cancer cells. Prolonged incubation of primary cell cultures of human oesophageal cancers as well as of the squamous oesophageal cancer cell line Kyse-140 with ATP or its stable analogue ATP gamma S dose-dependently inhibited cell proliferation. This was due to both an induction of apoptosis and cell cycle arrest. The expression of P2-receptors was examined by RT-PCR, immunocytochemistry, and [Ca(2+)](i)-imaging. Application of various extracellular nucleotides dose-dependently increased [Ca(2+)](i). The rank order of potency was ATP=UTP>ATP gamma S>ADP=UDP. 2-methylthio-ATP and alpha,beta-methylene-ATP had no effects on [Ca(2+)](i). Complete cross-desensitization between ATP and UTP was observed. Moreover, the phospholipase C inhibitor U73122 dose-dependently reduced the ATP triggered [Ca(2+)](i) signal. The pharmacological features strongly suggest the functional expression of G-protein coupled P2Y(2)-receptors in oesophageal squamous cancer cells. P2Y(2)-receptors are involved in the antiproliferative actions of extracellular nucleotides. Thus, P2Y(2)-receptors are promising target proteins for innovative approaches in oesophageal cancer therapy.

[Prevalence of obesity in children: study in the primary public Parisian schools]. / Prévalence de l'obésité chez l'enfant: étude dans les écoles primaires publiques parisiennes.

Obesity is an important risk factor in public health. In Paris, few statistical data are available in this area. The purpose of the present study is to evaluate the prevalence of overweight and obesity in 10 years-old children attending Paris elementary schools (cours moyen deuxième année--CM2--last level of the elementary school). 148 classes were randomly selected, gathering 3,621 schoolchildren 10 years 6 months old. 66 doctors in charge of health at school participated in the study, doing the measurements of weight, size and collecting also the weight and size at birth and at the "grande section-GS-level" (last level of the infant school, 5 years-old children) from the individual health file of the schoolchildren. The statistical analysis was based on the study of distributions of the observed Quetelet index (Q0) at the different ages, compared to French reference curves. A logistic regression analysis was performed to determine whether birth weight and GS weight predict obesity in CM2. In GS and in CM2, observed Quetelet indices are over expected values: in CM2, 22.8% of boys and 25.6% of girls exceed the reference value Q90; the prevalence of obesity (Q0 > or = Q97) is 13.4% in boys and 13.5% in girls. Among the variables "term", "weight at birth", weight in GS level and "gender", the weight in GS level is the only predictive factor of obesity in CM2 level. The situation in Paris appears to be serious. Preventive actions are needed at early stages to try to stop and, if possible, to reverse the present increase of overweight. In this context, school doctors have to play a prominent role.

Growth inhibition and apoptosis induced by P2Y2 receptors in human colorectal carcinoma cells: involvement of intracellular calcium and cyclic adenosine monophosphate.

Extracellular nucleotides induce apoptosis and inhibit growth of colorectal cancer cells. To understand the underlying signaling pathways, we investigated the role of nucleotide-sensitive P2 receptors and focused on the receptor-mediated signaling of intracellular Ca2+ and cyclic adenosine monophosphate (cAMP) in two colorectal carcinoma cell lines (HT29, Colo320 DM). Expression and functionality of P2 receptor subtypes evaluated by RT-PCR and [Ca2+]i imaging revealed that solely metabotropic P2 receptors of the subtype P2Y2 were expressed on a functional level in both cell lines. Short-term stimulation of P2Y2 receptors caused Ca2+ mobilization from intracellular stores and a subsequent transmembrane Ca2+ influx. The receptor-induced [Ca2+]i elevation was shown to increase basal-stimulated [cAMP]i moderately and to potentiate forskolin-stimulated [cAMP]i vigorously, since the effects were dose-dependently inhibited by preloading the cells with the [Ca2+]i chelator BAPTA. In contrast, activation of protein kinase C (PKC) did not contribute to a receptor-mediated rise in [cAMP]i, since the PKC inhibitor staurosporine completely failed to reduce P2Y2 receptor-induced increases in [cAMP]i. Prolonged application of P2Y2 receptor agonists induced a time-dependent increase in apoptosis (up to 50% above control values) in both cell lines and caused dose-dependent inhibition of cell proliferation of up to 85% (Colo320 DM) or 64% (HT29). Chelating [Ca2+]i with BAPTA almost completely abolished P2Y2 receptor-induced cell death. Rises in [cAMP]i elicited by either forskolin or cAMP derivatives inhibited growth in both cell lines, too. In line with the potentiating effect of P2Y2 receptors on forskolin-stimulated [cAMP]i increases, costimulation with forskolin and P2Y2 receptor agonists led to synergistic antiproliferative effects. Moreover, a synergistic growth inhibition was observed when coincubating the cells with the P2Y2 receptor agonist ATP and the cytostatic drug 5-fluorouracil, which forms the basis for most currently applied chemotherapeutic regimes in colorectal cancer treatment. Our results demonstrate the growth inhibitory potency of P2Y2 receptors in colorectal carcinoma cells. Receptor-induced [Ca2+]i signaling appears to play a major role in the observed antiproliferative and apoptosis-inducing effects.

Differential expression of matrix metalloproteinases and their tissue inhibitors in colon mucosa of patients with inflammatory bowel disease.

BACKGROUND/AIMS: Alterations in synthesis and breakdown of extracellular matrix components are known to play a crucial role in tissue remodelling during inflammation and wound healing. Degradation of collagens is highly regulated by a cascade of matrix metalloproteinases (MMPs). The current study was therefore designed to determine gene expression patterns of MMPs and their tissue inhibitors (TIMPs) in single endoscopic biopsies of patients with inflammatory bowel disease (IBD). PATIENTS/METHODS: mRNA expression was measured by quantitative competitive polymerase chain reaction (PCR) in biopsies from patients with ulcerative colitis (n=21) and Crohn's disease (n=21). Protein expression was analysed by western blotting and immunohistochemistry. RESULTS: MMP-2, MMP-14, and TIMP-1 mRNAs were marginally increased in inflamed, but 9-12-fold increased in ulcerated colonic mucosa in IBD whereas TIMP-2 mRNA expression remained unchanged. MMP-1 and MMP-3 mRNA expression correlated well with the histological degree of acute inflammation, resulting in more than 15-fold increased MMP-1 and MMP-3 mRNA levels in inflamed versus normal colon samples from patients with ulcerative colitis and Crohn's disease. CONCLUSION: Profound overexpression of MMP-1 and MMP-3 mRNA transcripts suggests an important role for these enzymes in the process of tissue remodelling and destruction in inflammatory bowel disease.

[beta-Catenine as a genomic target of high-grade microsatellite instability in colorectal cancer]. / beta-Catenin als genomischer Zielort der hochgradigen Mikrosatelliteninstabilität in kolorektalen Karzinomen.

AIMS: Various inherited and acquired alterations affecting the genes and gene products of the WNT pathway appear to be involved in the different molecular routes leading to colorectal cancer (CRC). This study was initiated to investigate the prevalence of somatic mutations in the beta-catenin gene (CTNNB1) and the associated pathology in CRC with defective DNA mismatch repair. METHODS: Paraffin and/or frozen sections of 33 primary CRC (including any liver and lymph node metastases present) with high-grade microsatellite instability (MSI-H; i.e. with > or = 5 unstable microsatellite markers of 10 tested) were polytopically fractionated by microdissection. Genomic and c-DNA samples were sequenced across exons 2-4 of CTNNB1 and the expression patterns of beta-catenin (beta-C) analyzed by immunohistology and Western blotting. RESULTS: Seven somatic mutations affecting phosphorylation sites of exon 3 (2 deletions also encompassing parts of either intron 2 or exon 4 [delta X2/3 bzw. delta X3/4] and 5 missense mutations [2 x T41A, 2 x S45F, S45P]) were identified. Two mutations (delta X3/4 and S45F) were concordantly present in CRC primaries and their respective metastases whereas the S45P mutation was restricted to a hepatic metastasis. In the delta X2/3 CRC primary only a shortened 66 kD CTNNB1 gene product was present while its associated liver metastasis showed a total loss of beta-C expression. CONCLUSIONS: Both exon 3 and the entire locus coding for beta-C are somatically altered in approximately 20% of CRC with MSI-H at different stages of tumor progression. Thus CTNNB1 appears to be a genomic target for complex oncogenic mutations and deletional processes in a substantial fraction of this molecular subset of CRC.

Clinical significance of Y chromosome loss in hematologic disease.

We have studied 215 male patients (aged 45-97 years) whose sole cytogenetic abnormality was clonal loss of the Y chromosome in metaphase cells from unstimulated cultures. The patients comprised a control group with no evidence of hematologic disease and four disease case groups: 1) myelodysplastic syndrome (MDS), refractory anemia, refractory anemia with excess blasts (RAEB), RAEB in transformation, and chronic myelomonocytic leukemia; 2) acute myelogenous leukemia; 3) myeloproliferative disorder (MPD), chronic granulocytic leukemia, and polycythemia vera; and 4) B-cell lymphoma/leukemia. The frequency of cells with Y loss increased with age and was significantly greater in cases than in controls, but it was not correlated with survival or with prior therapy. The frequency of cases with a -Y clone was 6.3% of male karyotypes and represented 16.4% of all abnormal male cytogenetic reports. Much of the difference between cases and controls appears to be accounted for by a greater frequency of cases with > 75% Y loss. A value of 81% chromosome Y loss maximized the combined sensitivity (28%) and specificity (100%) for predicting disease status, but a 75% cutoff provided the best estimate of disease risk. Even in older males, if > 75% of metaphase cells are 45,X,-Y, they probably represent a disease-associated clonal population, and it is possible that the critical genetic change is not visible through the microscope. This observation is true for MDS, MPD, B-cell disease, and especially acute myelogenous leukemia. The prognostic association of Y chromosome loss for survival appears to be neutral or favorable. Genes Chromosomes Cancer 27:11-16, 2000.

Effect of fusidic acid on the hepatic cytochrome P450 enzyme system.

OBJECTIVE: To investigate the effects of fusidic acid therapy on the hepatic cytochrome P450 (CYP450) enzyme system. METHODS: Thirty HIV-seropositive L-methadone-substituted i.v. drug abusers (stage CDC/WHO B2 - 3 with CD4+-counts ranging from 65 to 293/microl) were randomized into 3 groups (A - C). Ten patients were treated with fusidic acid 500 mg/day over a period of 14 (group A) or 28 days (group B), respectively. Patients in group C served as a control group and did not receive any medication apart from L-methadone. In order to investigate the hepatic monooxygenase system, pharmacokinetics were determined in all patients before initiation and 14 and 28 days after starting therapy with fusidic acid. The concentration of antipyrine and its 3 main metabolites (norantipyrine (NORA), 4-hydroxyantipyrine (OHA), 3-hydroxymethylantipyrine (HMA)) in plasma and urine were measured by high-performance liquid chromatography (HPLC). RESULTS: No effects on antipyrine pharmacokinetics and pharmacokinetics of antipyrine metabolites were found in group A after 14 days of fusidic acid intake and in the control group without therapy. However, in contrast an activation of the CYP450 enzyme system was observed in group B after 28 days of fusidic acid therapy with an increase of total antipyrine clearance (43.0 +/- 7.62 ml/min to 51.0 +/- 9.03 ml/min) as well as clearances to all metabolites (NORA 7.11 +/- 1.75 to 8.60 +/-2.10 ml/min, OHA 11.5 +/- 2.89 to 14.0 +/- 3.97 ml/min, HMA 4.05 +/- 0.99 to 4.94 +/- 1.27 ml/min). Antipyrine half-life was significantly reduced (12.3 +/- 2.8 h to 9.4 +/- 2.2 h) and some patients developed clinical signs of L-methadone underdosage. CONCLUSIONS: Our results suggest that fusidic acid has a time-dependent activating effect on the CYP450 enzyme system. Especially in treatment of patients who are frequently under multidrug regimens such as HIV-positive patients drug interactions should be taken into consideration.

Microsatellite alterations in serum DNA of patients with colorectal cancer.

Cell-free DNA in the blood of cancer patients has been shown to harbor microsatellite alterations frequently matching those of the primary tumors. The aim of this study was to assess the prevalence of allelic loss and instability of serum DNA microsatellites in colorectal cancers. DNA extracted from preoperative sera and microdissected tumors of 27 patients with colorectal adenocarcinoma were allelotyped for nine markers on chromosome arms 1p, 5q, 8p, 12p, 15q, 17p, 17q, and 18q. In all tumors, expression of MLH1 and MSH2 was explored immunohistochemically. Microsatellite alterations comprising loss of heterozygosity (LOH) or microsatellite instability (MSI) were present in 26 of 27 (96%) tumors and in 16 of 27 (59%) serum samples. Using stringent criteria, serum MSI was significantly (p < 0.02) more detectable than serum LOH. Of the three patients with high-grade MSI (more than two unstable loci) present in tumor and serum DNA, two had MSH2-negative tumors on immunohistochemical testing. No significant association of tumor stage or clinical outcome with serum microsatellite alterations of LOH or MSI type could be demonstrated. Although the DNA-shedding phenotype of tumors remains to be elucidated, its detection by serum DNA microsatellite analysis seems to be useful for the diagnosis and monitoring of neoplasms, including colorectal cancers with and without MSI.

Effects of antipsoriatic therapies on hepatic microsomal enzyme activity in patients with psoriasis.

OBJECTIVE: The influence of several antipsoriatic therapies on microsomal enzyme activity was assessed by comparing measurements of antipyrine kinetics prior to and two weeks after initiation of therapy. METHODS: Serum and urine analysis was carried out by means of high performance liquid chromatography (HPLC). Each form of therapy was examined separately. 10 patients were treated with etretinate. The groups treated with 8-methoxypsoralene (8-MOP) in combination with UVA irradiation (PUVA), etretinate in combination with PUVA (RePUVA), anthralin, or combined UVA and UVB irradiation (SUP) consisted of 7 patients each. RESULTS: Neither anthralin nor SUP therapy led to any significant changes in antipyrine kinetics. Antipyrine clearance under the other regimens was, however, reduced. It was 23% lower in PUVA-treated patients, 20% lower in those receiving retinoids and 28% lower in those under RePUVA (p<0.05 - 0. 01). CONCLUSIONS: PUVA, etretinate and RePUVA inhibit microsomal enzyme activity in the liver. Possible drug interactions with other P subset450 inducing or inhibiting agents should be considered in the therapy of psoriatic patients.

Changes of antipyrine pharmacokinetics during influenza and after administration of interferon-alpha and -beta.

OBJECTIVE: During viral infections serum levels of interferons are elevated. In this study we wanted to observe the effects of endogenous interferon (IFN) during an acute viral infection (influenza) and after external application of interferons on the pharmacokinetics of antipyrine which is a parameter of hepatic cytochrome P450 enzyme activity. METHODS: Endogenous plasma levels of interferons and the antipyrine pharmacokinetics in 10 otherwise healthy volunteers were investigated before outbreak and in the symptomatic interval of an acute viral respiratory infection. The serum interferon levels were determined by RIA. In another trial 2 groups of 9 HIV patients each in stage CDC/WHO B2/3 received low-dose interferon therapy with 0,75 Mio. I.U. interferon-alpha or -beta s.c./die. The concentrations of antipyrine in serum were measured by HPLC. The antipyrine kinetics were determined before the infection or the interferon therapy, respectively, and during viral infection or during interferon or after interferon therapy, respectively. RESULTS: The plasma levels of IFNalpha and IFNgamma were significantly elevated from 4.7 U/ml to 12.6 U/ml and 0.3 U/ml to 3.4 U/ml, respectively, whereas the antipyrine clearance showed a decrease from 57.9 ml/min to 45 ml/min in the symptomatic interval of an acute viral infection. During therapy with low-dose interferons we observed a significant difference after 12 week treatment with IFNalpha or IFNbeta, respectively. In the first group we observed a decreased antipyrine clearance from 49.0 ml/min to 41.7 ml/min; in the second group the antipyrine clearance decreased from 49.0 ml/min to 41.7 ml/min. CONCLUSION: Viral infections (influenza) are able to inhibit the hepatic monooxygenase system due to elevated serum interferon levels. Low doses of exogenous interferons inhibit the cytochrome P450 monooxygenase system.

Effect of zidovudine therapy in patients with HIV infection on endogenous interferon plasma levels and the hepatic cytochrome P450 enzyme system.

In this study, we wanted to investigate if there are differences in endogenous interferon (IFN) plasma levels in patients with different stages of HIV infections before and after therapy with zidovudine (ZDV) and determined the influence of ZDV therapy on the hepatic monooxygenase system by measuring the antipyrine pharmacokinetics. Therefore we investigated the endogenous IFN plasma levels in patients with asymptomatic HIV infection (CDC/WHO A1, n = 10) and patients with AIDS (CDC/WHO C3, n = 10). In AIDS plasma IFN-alpha and IFN-gamma levels are elevated (15.6 +/- 5.8 U/ml; 2.1 +/- 0.7 U/ml) compared to patients with an asymptomatic HIV infection (6.1 +/- 3.3 U/ml; 0.6 +/- 0.3 U/ml). The antipyrine clearance was significantly reduced in the group of AIDS patients (43.1 +/- 7.2 ml/min compared to 56.4 +/- 8.7 ml/min). In a second study with 11 patients in stage CDC/WHO A1/2 and CDC/ WHO B/C3 each, we studied the effect of a 14-day administration of ZDV on the endogenous plasma IFN levels and the CYP450 enzyme activity using the antipyrine pharmacokinetics as a parameter. We investigated the antipyrine clearance, clearance to metabolite and half-life by using HPLC. IFNs were measured by RIA or ELISA, respectively. In the first group no significant alterations of antipyrine kinetics or plasma IFN levels were observed after treatment with ZDV. In contrast to these results, we found a significant decrease in IFN-alpha and IFN-gamma (19.8 +/- 3.6 U/ml, 4.6 +/- 1.5 U/ml before; 7.9 +/- 2.6 U/ml, 1.9 +/- 1.3 U/ml after administration of ZDV), a decrease in antipyrine half-life, an elevation of the antipyrine clearance (49.8 +/- 15.7 ml/min, 57.3 +/- 13.7 ml/min) and an elevation of the clearances to metabolite.

Clinical manifestations and therapies of AIDS associated tumors.

We are giving an overview over the clinical features and different therapeutic options of HIV associated malignancies. There are three AIDS-defining malignancies: - Kaposi's sarcoma - Non-Hodgkin's lymphoma (NHL) - cervical cancer. In Kaposi sarcoma there is a broad therapeutic spectrum from cryotherapy to systemic chemotherapy depending on the site and stage of the Kaposi sarcoma. In NHL early therapeutic intervention is necessary because of the fast progress of the tumor. The cervical cancer in HIV-infected women seems to be more aggressive than in non-infected and also needs early therapeutic intervention. Many other tumors seem to occur more frequently in patients with HIV infection: anorectal cancer, malignant testicular tumors, lung cancer, Hodgkin's lymphoma, basal cell carcinoma, squamous cell carcinoma, and even malignant melanoma. The cancer incidence in HIV-patients seems to be higher among nonblacks. Most of the immunodeficiency associated tumors are virus induced and they are accompanied by a persistent viral infection, including HHV-8 in Kaposi's sarcoma; Epstein Barr virus (EBV) in NHL; and human papillomavirus (HPV) in cervical cancer. But there are also types of virus induced tumors which are not frequently associated with HIV-infection like the primary hepatocellular carcinoma in patients with hepatitis B virus infection.

Pharmacokinetic interaction of fluconazole and zidovudine in HIV-positive patients.

To investigate the interaction of fluconazole and zidovudine in HIV-positive non-smoking male patients with AIDS categorized as CDC group IV we studied two groups, each consisting of 10 male, non-smoking, HIV-positive patients with CDC group IV disease, with the patients in the first group additionally suffering from candida esophagitis. In the first group, the pharmacokinetics of 500 mg oral zidovudine were determined both before and after 7 days of treatment with fluconazole 400 mg/d. In the second group, the pharmacokinetics of 200 mg oral fluconazole were determined before and after 14 days of treatment with zidovudine 4 x 250 mg/d. In order to determine the microsomal enzyme activity, the 6-beta-hydroxycortisol/17-hydroxycorticosteroid ratio and antipyrine pharmacokinetic parameters were determined. 6-beta-hydroxycortisol was quantitated by RIA. The 17-hydroxycorticosteroids were determined by a colorimetric method. Zidovudine (ZDV) and zidovudine glucuronide (GZDV), and the fluconazole and antipyrine plasma and urine concentrations were measured by HPLC. Administration of fluconazole resulted in a significant increase in the half-life of zidovudine and antipyrine (0.97 +/- 0.17 h prior to vs. 1.11 +/- 0. 14 h after fluconazole administration and 11.9 +/- 1.9 h prior to vs. 13.7 +/- 3.0 h after fluconazole, respectively) while the 6-beta-hydroxycortisol excretion decreased significantly (472.3 +/- 80.6 microg/24 h before and 340.6 +/- 82.1 microg/24 h after administration of fluconazole). No changes were found in the GZDV plasma kinetics and the ZDV and GZDV urinary excretion. Treatment with ZDV did not have any impact on the half-life of fluconazole. Administration of zidovudine did, however, result in a significant reduction in antipyrine half-life (11.7 +/- 2.0 h before vs. 9.9 +/- 2.3h after ZDV) and a significant increase in 6-beta-hydroxycortisol excretion (438,7 +/- 138.2 microg/24 h before and 684.6 +/- 157.3 microg/24 h after ZDV). Since the antipyrine clearance is altered after administration of ZDV, it is assumed that zidovudine induces cytochrome P450 enzymes. This effect, however, does not alter the pharmacokinetics of fluconazole. High doses of fluconazole can inhibit the plasma elimination of both antipyrine and zidovudine, but the extent of this inhibitory effect is so small that no clinically relevant accumulation is to be expected.

Effects of thyroid and growth hormone deficiency, and food restriction on heart mass, with and without added stress (carboxyhemoglobinemia).

The roles of thyroid and growth hormone, and food restriction in maintenance of heart mass and in carbon monoxide-stimulated cardiac growth were examined. First, thyroidectomized and normal adult male rats inhaled up to 500 ppm CO in air for 42 days. Combined ventricular weights of thyroidectomized rats inhaling CO and air were 12 and 23% smaller than predicted, respectively, while the combined ventricular weight of normal rats inhaling CO was 29% larger than predicted. Thyroidectomy increased the mass of the left ventricle relative to the right ventricle; this was reversed by CO treatment. While the hematocrit increased in thyroidectomized-CO rats, it was lower than in normal-CO rats: likewise the hematocrit of thyroidectomized-AIR rats was lower than that of normal rats in air. Body weights of the thyroidectomized rats were 57% that of normals. As additional controls, two groups of normal rats (one AIR, one CO) were maintained at the same body weight as the thyroidectomized rats, by adjusting food intake. Combined ventricular weight was less than predicted in AIR rats and failed to increase in CO animals, while hematocrits were the same as normals in air and in CO. Serum thyroxine (T4) and growth hormone levels assayed in thyroidectomized rats were less than 15 and 25% of normal rats, respectively. Growth hormone levels were not altered by CO inhalation in thyroidectomized and in normal rats. Levels of both hormones were normal in food-restricted rats. While thyroidectomy produced cardiac atrophy, cardiac growth was stimulated by CO inhalation, although heart mass then only approached that of normals in air. Food restriction also produced cardiac atrophy, but CO inhalation failed to stimulate heart growth.

Cardiac compliance and dimensions in carbon monoxide-induced cardiomegaly.

Adult male rats inhaled 500 ppm CO continuously for 38 to 47 days to produce significant cardiomegaly. In a first experiment in which heart wall stiffness was examined, haematocrit rose 45.1% and the ratio of the sum of right ventricle (RV) and left ventricle (LV) to body weight (mg X g-1) increased from 2.69 to 3.34. Compliance (ml X mmHg-1) of CO LV's and RV's studied from 0 to 25 mmHg intraluminal pressure, was generally greater than that of LV's and RV's from controls at the same pressure. These differences were greater for RV's. There was no difference between control RV's and LV's at the same distending pressure. The differences between treated and control groups disappeared when compliance was normalised per g heart weight. In a second experiment in which heart dimensions were examined, haematocrit ratio increased 48.6% and 2V (RV + LV) to body weight ratio (mg X g-1) increased from 2.77 to 3.45. Atrial weight was also greater. LV apex to base length increased 6.4% and LV outside diameter increased 7.3. No significant differences in LV, RV or interventricular septum (S) thickness resulted from CO exposure, as measured at three sites in each, in four cross-sections of the heart between the apex and base. In general, LV wall was slightly thicker than S, while RV was about 35% that of LV. The findings suggest that chronic carboxyhaemoglobinaemia produces largely eccentric cardiomegaly, and that there is no intrinsic change in wall stiffness.