Reiko Demura

Effects of Chlorpromazine and Naloxone on Growth Hormone Secretion in Rats

The present study was conducted to examine roles of brain monoamines and opioid peptides in growth hormone (GH) secretion in unanesthetized, freely behaving rats. The administration of chlorpromazine (CPZ, 300 microgram/100 g, i.v.), an antagonist of brain monoamines, to rats that were passively immunized with antiserum to somatostatin immediately lowered plasma GH levels and inhibited episodic GH secretion. An intraventricular injection of beta-endorphin (3.5 microgram) stimulated GH secretion. This effect was completely inhibited by the prior administration of naloxone (100 microgram/100 g, i.v.), a specific antagonist of opioid peptides, but not by CPZ. In addition, the administration of naloxone did not inhibit episodic GH secretion. The results suggest that CPZ inhibits episodic GH secretion via a factor(s) other than somatostatin. It is also inferred that brain monoamines, but not opioid peptides, play major roles in the regulation of episodic GH secretion in rats.

INDUCTION OF HEME OXYGENASE PRODUCES LOAD-INDEPENDENT CARDIOPROTECTIVE EFFECTS IN HYPERTENSIVE RATS

Although heme oxygenase (HO) has been suggested to be involved in the regulation of cardiovascular function through production of carbon monoxide (CO), the pathophysiological significance of HO in hypertensive organ damage remains unknown. We examined the effects of inducing HO-1 mRNA by stannous chloride (SnCl2) on cardiac hypertrophy in stroke-prone spontaneously hypertensive rats (SHR-SP/Izm). Chronic administration of SnCl2 resulted in a significant decrease in left ventricular (LV) weight/body weight ratio and LV brain natriuretic peptide (BNP) mRNA levels as a marker of cardiac hypertrophy and a significant increase in LV HO-1 mRNA levels and LV cGMP contents in SHR-SP/Izm, while there was no significant change in systemic blood pressure. These results provide the first evidence that induction of HO in the heart attenuates cardiac hypertrophy in load-independent mechanism in genetically hypertensive rats.

Effect of Hemodialysis on the Concentration of the Seven Tumor Markers Carcinoembryonic Antigen, Alpha-Fetoprotein, Squamous Cell Carcinoma-Related Antigen, Neuron-Specific Enolase, CA 125, CA19–9 and CA 15–3 in Uremic Patients

The incidence of the 7 tumor markers carcinoembryonic antigen (CEA), alpha-fetoprotein (AFP), squamous cell carcinoma-related antigen (SCC), neuron-specific enolase (NSE), CA 125, CA 19-9 and CA 15-3 was studied before and after hemodialysis (HD) in 144 uremic patients who had no malignancies. Before HD, of all tumor markers, the mean concentration of SCC only exceeded the normal value. The positive rate was highest in SCC (95.1%), and that of CEA and NSE was 25.7 and 10.6%, respectively. However, AFP was within the normal range in all cases. Among CA antigens, the positive rate of CA 125 was 7.6%, of CA 19-9 was 6.3% and of CA 15-3 was 3.5%. After HD, the incidence as well as the mean concentration of all tumor markers increased. A parallel increment of total protein was observed after HD. The membrane filter used in HD appears to be insufficient to remove tumor marker proteins during HD. It is necessary to consider the clinical interpretation of elevated tumor markers in patients with uremia.

Deferential roles of angiotensin receptor subtypes in adrenocortical function in mice

The functional significance of angiotensin II (Ang II) receptor subtypes in adrenals remains unknown. Ang II receptor type 1a (AT1a) expression was localized by in situ hybridization to the zona glomerulosa and zona fasciculata, while AT1b was localized to the zona glomerulosa. Plasma aldosterone and corticosterone levels were measured after injection with Ang II or the type 2 receptor (AT2) agonist CGP-42112 in wild-type and AT1a deficient mice. Aldosterone and corticosterone levels were lower in AT1a deficient mice. Ang II increased plasma aldosterone levels in AT1a deficient mice, but to a lesser extent in mice pretreated with nonselective AT1a/AT1b antagonist, CV-11974. CGP-42112 did not affect aldosterone levels. Ang II increased corticosterone levels in wild-type mice but not in AT1a deficient mice. Results suggest Ang II stimulates aldosterone secretion via AT1a and AT1b in the zona glomerulosa and corticosterone secretion via AT1a in the zona fasciculata, and provide first evidence for differential roles of AT1a and AT1b in the adrenals.

Effects of two calcium channel blockers on messenger RNA expression of endothelin-1 and nitric oxide synthase in cardiovascular tissue of hypertensive rats

OBJECTIVE The aim of this study was to investigate the effects of calcium channel blockers on messenger RNA expression of endothelin-1 and endothelial-type nitric oxide synthase in the cardiovascular tissue of stroke-prone spontaneously hypertensive rats (SHRSP). MATERIALS AND METHODS The calcium channel blocker nilvadipine (1.0 or 3.2 mg/kg per day) was subcutaneously administered to two groups of SHRSP, from 4 or 8 weeks of age, for 8 weeks and 4 weeks, respectively. For comparison, nifedipine (3.2 mg/kg per day) was similarly administered to SHRSP from 4 weeks of age for 8 weeks. Kidney, heart, aorta and brain tissue samples were obtained when the rats were 12 weeks old. Messenger RNA expression of endothelin-1 and endothelial-type nitric oxide synthase was determined by reverse transcription-polymerase chain reaction followed by Southern blotting and a ribonuclease protection assay, respectively. Results were compared with those in untreated SHRSP and Wistar-Kyoto rats at 12 weeks of age. RESULTS Both nilvadipine and nifedipine significantly decreased blood pressure in SHRSP. Although there were no changes in the weights of the kidney and brain, there was a significant decrease in the weight of the left ventricle of the groups treated with nilvadipine (1.0 mg/kg per day: mean +/- SEM 0.282 +/- 0.003 g; 3.2 mg/kg per day: 0.269 +/- 0.005 g) and nifedipine (1 mg/kg/day: 0.281 +/- 0.012 g) for 8 weeks compared with untreated SHRSP (0.301 +/- 0.004 g). Endothelin-1 messenger RNA expression, which was significantly increased by about twofold in the kidney, heart and brain of SHRSP compared with Wistar-Kyoto rats, was normalized by both calcium blockers. Endothelin-1 messenger RNA expression, which was decreased in the aorta of SHRSP, was further decreased by both calcium blockers. While there was no significant difference in endothelial-type nitric oxide synthase messenger RNA expression in the kidney, heart and aorta between the untreated SHRSP and Wistar-Kyoto rats, expression in the aorta was significantly increased in the group treated with these calcium blockers for 8 weeks from 4 weeks of age. CONCLUSIONS These results suggest that, in addition to their potent antihypertensive effects, calcium channel blockers may exhibit cardiovasculoprotective and renoprotective effects by modifying mRNA expression of endothelin-1 and endothelial-type nitric oxide synthase in tissue.

Steroid receptors in dimethylhydrazine-induced colon carcinogenesis

To investigate whether gonadal hormones are involved in the tumorigenesis of dimethylhydrazine (DMH)‐induced colonic neoplasms, the authors measured steroid receptors in the neoplasms. 30‐ or 60‐day‐old BD‐IX rats were injected with 20 mg of 1,2‐DMH per kg of body weight once a week for 20 weeks. Fifty‐seven rats were sacrificed at 40 to 45 weeks after the initial injection. Androgen receptor (AR), estrogen receptor (ER), and progesterone receptor (PR) were measured in colonic neoplasms. The total number of colonic neoplasms was 274 among 57 rats, 65.8% in male rats and 34.2% in female rats. The mean number of colonic neoplasms per rat was higher in male rats, i.e., 5.6, compared with 3.5 in female rats. A slightly higher number of colonic neoplasms per rat was seen in the rats that had the initial injection at 30 days of age. The number of large colonic neoplasms with a diameter of more than 1 cm was 77 (28.1%), 74% of which were seen in male rats. Thus, a higher incidence of tumors that were also larger were seen in male rats. Histologic findings showed that 53.6% of the neoplasms were carcinomas. The highest incidence of colonic neoplasms was in the distal colon in both sexes. Most of the well‐differentiated adenocarcinoma were seen in the distal colon (82.2%), whereas mucinous carcinoma and undifferentiated adenocarcinoma were prominent in the proximal colon or cecum (56.1%). In rats with a normal colon, low levels of AR and PR were determined; but ER was not found in any regions of the colon. In DMH‐induced colonic cancer, the incidence as well as the concentration was higher in male rats (60.6%, 16.9 ± 3.6 fm/mg protein), compared with female rats (40.0%, 4.6 ± 0.8 fm/mg protein). Similar incidences and levels of ER and PR were seen in both sexes. There was no relationship between steroid receptors and histologic findings in colonic neoplasms. These results suggest that the gonadal hormones, especially androgens, appear to be involved in DMH‐induced colon tumorigenesis in male rats.

Steroid receptors and the distribution of IR-carcinoembryonic antigen in colonic cancer.

Twenty-five colonic cancer tissues were studied for the presence of estrogen and progesterone receptors (ER, PR) and the distribution of immunoreactive carcinoembryonic antigen (IR-CEA). ER and PR were determined in 6 (24 per cent) and 3 (12 per cent), respectively, of 25 patients with colonic cancer. Of the six patients with ER, five were females, four of whom were postmenopausal. Steroid receptors, however, had no correlation with age, tumor localization, stage of disease or IR-CEA. In cancer tissue, IR-CEA in the cytosol fraction was higher than that found in the membrane fraction. In normal colon, however, the concentrations of the two fractions were reversed. Immunohistochemical findings have shown a different distribution of IR-CEA in cancerous and normal colon, and our results demonstrated similar findings by using radioimmunoassay (RIA).

Plasma groeth hormone and thyrotropin responses to thyrotropin releasing hormone in freely behaving and urethane anesthetized rats

Abstract Plasma GH and TSH responses to thyrotropin releasing hormone (TRH) were examined in freely behaving and urethane anesthetized rats. The i.v. administration of TRH (200ng/100g b.wt.) resulted in consistent elevations of plasma GH only in urethane anesthetized rats, while significant elevations of plasma TSH were similarly observed in both conditions. Results suggest that urethane influences plasma GH responses to TRH.

Gene expression of endothelin-1 and endothelial-type nitric oxide synthase in cardiovascular tissues of stroke-prone spontaneously hypertensive rats/Izm: effects of the angiotensin-converting enzyme inhibitor aracepril.

We studied target organ-protective effects of aracepril, an angiotensin-converting enzyme inhibitor, and the expression of endothelin-1 (ET-1) and nitric oxide synthase (NOS) mRNA. Aracepril (30 mg/kg) was administered orally to Izumo strain of stroke-prone spontaneously hypertensive rats (SHR-SP/Izm) for 8 weeks from 4 weeks of age and for 4 weeks from 8 weeks of age. The expression of ET-1 and endothelial NOS (eNOS) mRNA in the heart, aorta, kidneys, and brain cortex, and the expression of neuronal NOS (bNOS) mRNA in brain cortex, were analyzed by RT-PCR/Southern blotting or RNase protection analysis. Administration of aracepril markedly lowered blood pressure and decreased left ventricular weight in SHR-SP/Izm. Expression of ET-1 mRNA in the heart, kidneys, and brain was significantly enhanced in SHR/SP/Izm compared with that in WKY/Izm. Aracepril significantly decreased the expression of ET-1 mRNA, whereas there was no significant change of that in the aorta. Although expression of eNOS mRNA in the heart, aorta, and kidneys did not show any significant difference between the two strains of rats, administration of aracepril for 8 weeks significantly decreased the expression of eNOS and bNOS mRNA in brain tissue. These results suggested that aracepril may protect major target organs by modifying the expression of ET-1 and NOS mRNA, in addition to its hypotensive effect.

Plasma Inhibin and Activin in Disease

The development of immunoassays for inhibin using heterologous radioim-munoassay (RIA) (1–3) or a synthetic N-fragment of the α-subunit (4) has allowed determination of the plasma concentration of immunoreactive inhibin and its role in human reproductive physiology. Specific measurement of different isoforms (5) or precursors of inhibins (6) has been reported in recent years, but the clinical usefulness of individual assay methods and the diagnostic significance of measuring circulating inhibin still remain controversial because of inconsistency in the assays. Recently, an ir-inhibin RIA kit manufactured by Nippon DPC of Japan, became available (7). The kit measures immunoreactive inhibin, a combination of dimeric inhibins and the α-subunit monomer, and is sensitive enough to define the normal range and specific enough not to cross-react with activin. This prompted us to measure plasma ir-inhibin levels in various pituitary, adrenal, gonadal, and other diseases in an attempt to find the clinical significance of inhibins and their pathophysiological role. At the same time, the plasma level of free activin was measured using a competitive protein-binding assay with follistatin (8).