Biomedical subjects

M Ohara

Publications and source records attributed to M Ohara.

At least 19 recordsLinked to original sources

PubMed2000

Neuronal nitric oxide synthase and systemic vasodilation in rats with cirrhosis.

Cirrhosis is typically associated with a hyperdynamic circulation consisting of low blood pressure, low systemic vascular resistance (SVR), and high cardiac output. We have recently reported that nonspecific inhibition of nitric oxide synthase (NOS) with nitro-L-arginine methyl ester reverses the hyperdynamic circulation in rats with advanced liver cirrhosis induced by carbon tetrachloride (CCl(4)). Although an important role for endothelial NOS (eNOS) is documented in cirrhosis, the role of neuronal NOS (nNOS) has not been investigated. The present study was carried out to specifically investigate the role of nNOS during liver cirrhosis. Specifically, physiological, biochemical, and molecular approaches were employed to evaluate the contribution of nNOS to the cirrhosis-related hyperdynamic circulation in CCl(4)-induced cirrhotic rats with ascites. Cirrhotic animals had a significant increase in water and sodium retention. In the aorta from cirrhotic animals, both nNOS protein expression and cGMP concentration were significantly elevated compared with control. Treatment of cirrhotic rats for 7 days with the specific nNOS inhibitor 7-nitroindazole (7-NI) normalized the low SVR and mean arterial pressure, elevated cardiac index, and reversed the positive sodium balance. Increased plasma arginine vasopressin concentrations in the cirrhotic animals were also repressed with 7-NI in association with diminished water retention. The circulatory changes were associated with a reduction in aortic nNOS expression and cGMP. However, 7-NI treatment did not restore renal function in cirrhotic rats (creatinine clearance: 0.76 +/- 0.03 ml. min(-1). 100 g body wt(-1) in cirrhotic rats vs. 0.79 +/- 0.05 ml. min(-1). 100 g body wt(-1) in cirrhotic rats+7-NI; P NS. ). Taken together, these results indicate that nNOS-derived NO contributes to the development of the hyperdynamic circulation and fluid retention in cirrhosis.

Animals↗

PubMed2000

Electrophysiologic analysis of antidepressant drug effects on the GABA(A) receptor complex based upon antagonist-induced encephalographic power spectrum changes.

To better understand antidepressant drug effects on the GABA(A) receptor complex (the GABA(A) receptor, chloride ionophore and benzodiazepine receptor), we investigated how antidepressants influenced power spectrum changes induced by pentylenetetrazol (PTZ), a chloride ionophore antagonist, in the rat hippocampal electroencephalogram (EEG). In control recording, PTZ (27.5 mg/kg i. p.) increased EEG power at frequencies under 12 Hz up to five times. After rats were pretreated with imipramine, fluoxetine or trazodone for 7 days (10 mg/kg i.p., twice a day), PTZ could not increase EEG power to more than three times the power before injection; this effect was not observed after pretreatment for 3 days. These three antidepressants inhibit serotonin uptake, while two other antidepressants, desipramine and nortriptyline, that inhibit norepinephrine uptake failed to counter the PTZ effect. We concluded that antidepressants with serotonergic effects enhanced the function of the GABA(A) receptor complex.

Animals↗

PubMed2000

Histochemical responses of human soleus muscle fibers to long-term bedrest with or without countermeasures.

Effects of 2- or 4-month bedrest in -6 degrees head-down tilt position with or without countermeasures on the histochemical properties of fiber phenotype and cross-sectional area (CSA) were studied in human soleus. The CSAs in slow fibers decreased approximately 32% during 4-month bedrest. This reduction was normalized after 1-month recovery. Although the reduction of percent slow fibers was not significant statistically, the percent intermediate fibers was significantly elevated 4 months after bedrest. Such shift in fiber type was not normalized following 1-month recovery. Effects of wearing an anti-g Penguin suit which has a modest, but continuous resistance at the knee and ankle (Penguin-1) or with knee resistance without loading on the ankle (Penguin-2) for 10 consecutive hours daily were also investigated during approximately 2 months of bedrest. The subjects performed knee extension and flexion for the last 15 min of each hour while in a supine position in bed. Bedrest-induced fiber atrophy was prevented in the Penguin-1 group but not the Penguin-2 group. Transformation of fiber type was not prevented in either Penguin suit group. It is suggested that long-term bedrest causes an atrophy and a shift of fiber phenotype toward fast-twitch type in human soleus. Data also indicated that loading on the muscle is an effective countermeasure for prevention of fiber atrophy but not fiber-type transformation.

Adult↗

PubMed2000

[Pretreatment of acid-induced lung injury with specific neutrophil elastase inhibitor ONO-5046 did not exasperate the subsequent bacterial lung infection by Pseudomonas aeruginosa].

Patients with acid lung injuries are at high risk for bacterial pulmonary infections which commonly occur several days after the acid aspiration. We reported that a specific neutrophil elastase inhibitor ONO-5046 inhibited the multi-organ injury caused by acid-instillation into the lung. In this study, we evaluated the effect of ONO-5046 on lung infection by Pseudomonas aeruginosa (PAO-1:Ps.) following acid-induced lung injury in rat lungs. Animals received 0.2 ml of hydrochloric acid (pH = 1) into the right lungs. Pretreated animals were administered ONO-5046 (30 mg.kg-1) i.v. 15 min. before acid instillation. Other groups received vehicle (saline). Twenty four hours later, they were instilled with 0.1 ml of Ps. 1 x 10(8) cfu into the left lungs. Four hours after bacterial challenge, the animals were deeply anesthetized and killed. Bronchoalveolar lavage was done on each lung separately to evaluate neutrophil elastase activity, neutrophil number and protein permeability of lung endothelium and epithelium. The numbers of Ps. in the lungs were measured. In the Ps.-instilled lung, the number of Ps. or the protein permeability was not increased with ONO-5046 pretreatment compared with those in the untreated group. Pretreatment inhibited the exasperation of the protein permeability indirectly caused by Ps. infection in the acid-instilled lung. It was indicated that ONO-5046 could inhibit the indirect lung injury caused by acid-instillation into the lung without aggravating the subsequent bacterial infection.

Animals↗

PubMed2000

Grafting of stomach tissue into the duodenum in F344 rats results in chimeric crypts and tumor development.

Gastric tissue was transplanted from the fundic and pyloric mucosa of 8-week old female F344 rats into the duodenum of males. Autopsy, 12 months after the operation, revealed grafts associated with persistent stones in the duodenum and/or calcification in the tissue. Pepsinogen positive chimeric glands with goblet cells also appeared in the grafts which gave rise to tumors in 18 out of 45 animals (40%). In conclusion, stomach grafts re-differentiate into intestine with goblet cells in the duodenum and this process predisposes to tumor development.

Animals↗

PubMed2000

[Arterial infusion chemotherapy for liver metastases from colorectal cancer--therapeutic effects of different protocols].

The therapeutic effects of different protocols for arterial infusion chemotherapy were compared in patients with multiple liver metastases from colorectal cancer. A total of 49 patients with colorectal multiple liver metastases treated in our hospital since 1988 were the subjects. In order to compare the therapeutic effects on the regression of cancer and the survival rate, the subjects were assigned into Groups A-D, which were treated using different protocols. Group A received ADR, EPI, CDDP or 5-FU alone at first. If this drug was not effective, it was replaced with another of those mentioned here, and so on. Group B received CDDP 50 mg on day 1, 5-FU 500 mg/day from day 2 to day 7 and 5-FU 500 mg/day for 2 weeks thereafter (FP treatment). Group C received CDDP 50 mg at the time of reservoir insertion and 5-FU 1,000 mg for 5 hours thereafter (WHF treatment). Group D received 5-FU 1,000 mg for 24 hours on day 1, day 3, and day 5 of every week with combination of CDDP 5-10 mg/day from day 1 to day 5 and none on day 6 and day 7 (intermittent F + low-dose P treatment) for 3 weeks. The response rate was 33% for Group A (n = 18), 46% for Group B (n = 13), 25% for Group C (n = 8) and 80% for Group D (n = 10), showing significant differences between Group D and other groups. The 1-year survival rate was 50% for Group A, 46% for Group B, 29% for Group C and 89% for Group D. Significant differences in survival rate were found between Group B and D, and Group C and D.

Antineoplastic Agents↗

PubMed1999

Intraoperative radiation therapy to the upper mediastinum and nerve-sparing three-field lymphadenectomy followed by external beam radiotherapy for patients with thoracic esophageal carcinoma.

BACKGROUND: In patients with thoracic esophageal carcinoma, radical dissection of the upper mediastinal lymph nodes often leads to complications such as recurrent laryngeal nerve palsy and subsequent pulmonary disorders. Intraoperative radiation therapy (IORT) to the upper mediastinum and nerve-sparing three-field lymphadenectomy followed by external beam radiotherapy has been developed to improve the locoregional control rate without resulting in these major postoperative complications. METHODS: Three-field lymphadenectomy, including cervical, mediastinal, and abdominal lymph node dissection, was performed. Dissection of the upper mediastinum was conservative to preserve recurrent laryngeal nerve function. IORT of 12-25 grays (Gy) was applied to the upper mediastinum. Postoperative radiation therapy (PORT) of 45 Gy in 16 fractions over 4 weeks was applied to the entire neck and upper mediastinum using an external X-ray beam. Between 1989-1996, 121 patients with thoracic esophageal carcinoma underwent surgery and received IORT, and 103 of these patients underwent PORT as part of their treatment schedule. RESULTS: The surgical mortality rate was 0.8% (1 of 121 cases). The overall 5-year survival rate was 34.4% and the cause specific 5-year survival rate was 54.8%. The cause specific 5-year survival rate for pN0 tumors was 79.4% and was 43.8% for pN1 tumors. No patients died with locoregional recurrence in the mediastinal lymph nodes. Recurrent laryngeal nerve palsy was observed in 25 patients (21%), but the palsy remained for > 1 month in only 13 patients (11%). Mechanical ventilation support for > 48 hours was required for 22 patients (18.2%). Fatal tracheal ulcers occurred in 4 of 18 patients who received the highest IORT dose of 25 Gy. CONCLUSIONS: Three-field lymphadenectomy to preserve recurrent laryngeal nerves and IORT using 12-20 Gy followed by 45-Gy PORT effectively reduced locoregional recurrence, recurrent laryngeal nerve palsy, and pulmonary complications caused by radical surgical dissections. The minimally effective dose of IORT appears to be < or = 15 Gy, a factor that will be further evaluated with longer follow-up.

Adult↗

PubMed1999

Active and passive immunization with the Pseudomonas V antigen protects against type III intoxication and lung injury.

Pseudomonas aeruginosa is an opportunistic bacterial pathogen that can cause fatal acute lung infections in critically ill individuals. Damage to the lung epithelium is associated with the expression of toxins that are directly injected into eukaryotic cells through a type Ill-mediated secretion and translocation mechanism. Here we show that the P. aeruginosa homolog of the Yersinia V antigen, PcrV, is involved in the translocation of type III toxins. Vaccination against PcrV ensured the survival of challenged mice and decreased lung inflammation and injury. Antibodies to PcrV inhibited the translocation of type III toxins.

Animals↗

PubMed1999

Identification and characterization of a new lipoprotein, NlpI, in Escherichia coli K-12.

We report here the identification of a new lipoprotein, NlpI, in Escherichia coli K-12. The NlpI structural gene (nlpI) is located between the genes pnp (polynucleotide phosphorylase) and deaD (RNA helicase) at 71 min on the E. coli chromosome. The nlpI gene encodes a putative polypeptide of approximately 34 kDa, and multiple lines of evidence clearly demonstrate that NlpI is indeed a lipoprotein. An nlpI::cm mutation rendered growth of the cells osmotically sensitive, and incubation of the insertion mutant at an elevated temperature resulted in the formation of filaments. The altered phenotype of the mutant was a direct consequence of the mutation in nlpI, since it was complemented by the wild-type nlpI gene alone. Overexpression of the unaltered nlpI gene in wild-type cells resulted in the loss of the rod morphology and the formation of single prolate ellipsoids and pairs of prolate ellipsoids joined by partial constrictions. NlpI may be important for an as-yet-undefined step in the overall process of cell division.

Amino Acid Sequence↗

PubMed1999

Myonuclear domain and myosin phenotype in human soleus after bed rest with or without loading.

After 2 or 4 mo of bed rest (6 degrees head-down tilt) and 1 mo of ambulation, there was a tendency toward a higher percentage of fibers expressing fast myosin heavy chain (MHC) isoforms and a de novo appearance of fibers coexpressing type I+IIa+IIx and IIa+IIx MHC in human soleus fibers. After 2 and 4 mo of bed rest, the mean size of type I fibers decreased by 12 (P > 0.05) and 39%, respectively. Because myonuclear number/mm of fiber length was unchanged, myonuclear domain was smaller after bed rest than before. The mean size and myonuclear domain of type I fibers were largest after 1 mo of recovery. The effects of wearing an antigravity device (Penguin suit), which had a modest but continuous resistance at the knee and ankle (Penguin-1) or knee resistance without loading on the ankle (Penguin-2), for 10 consecutive h/day were determined during 2 mo of bed rest. Mean fiber sizes in Penguin-1, but not Penguin-2, group were maintained at or above pre-bed-rest levels, whereas neither group showed phenotype changes. Myonuclear domain in type I fibers was larger in Penguin-1 and smaller in Penguin-2 group post- compared with pre-bed rest, indicating that a single daily 10-h bout of modest muscle loading can prevent bed-rest-induced soleus fiber atrophy but has minimal effect on myosin phenotype. The specific adaptive cellular strategies involved may be a function of the duration and magnitude of the adaptive stimulus as well as the immediate activity history of the fiber before the newly changed functional demands.

Adult↗

PubMed1999

Pathogenesis of septic shock in Pseudomonas aeruginosa pneumonia.

The pathogenesis of septic shock occurring after Pseudomonas aeruginosa pneumonia was studied in a rabbit model. The airspace instillation of the cytotoxic P. aeruginosa strain PA103 into the rabbit caused a consistent alveolar epithelial injury, progressive bacteremia, and septic shock. The lung instillation of a noncytotoxic, isogenic mutant strain (PA103DeltaUT), which is defective for production of type III secreted toxins, did not cause either systemic inflammatory response or septic shock, despite a potent inflammatory response in the lung. The intravenous injection of PA103 did not cause shock or an increase in TNF-alpha, despite the fact that the animals were bacteremic. The systemic administration of either anti-TNF-alpha serum or recombinant human IL-10 improved both septic shock and bacteremia in the animals that were instilled with PA103. Radiolabeled TNF-alpha instilled in the lung significantly leaked into the circulation only in the presence of alveolar epithelial injury. We conclude that injury to the alveolar epithelium allows the release of proinflammatory mediators into the circulation that are primarily responsible for septic shock. Our results demonstrate the importance of compartmentalization of inflammatory mediators in the lung, and the crucial role of bacterial cytotoxins in causing alveolar epithelial damage in the pathogenesis of acute septic shock in P. aeruginosa pneumonia.

Animals↗

PubMed1999

[Effects of propiverine hydrochloride (propiverine) on isolated rat and dog urinary bladder].

Propiverine is a drug for the treatment of incontinence and pollakiuria. The effects of propiverine on isolated rat and dog urinary bladder were investigated. At doses of 10(-6)-3 x 10(-5) M, propiverine caused both a rightward shift and inhibition of the maximum response in the acetylcholine (ACh) dose-response curve. The pA2 values for rat and dog urinary bladder were 5.97 and 6.62, respectively. At doses of 10(-5)-10(-5) M, propiverine also dose-dependently inhibited KCl (100 mM)-induced contractions. The IC50 values for rat and dog urinary bladder were 3.9 x 10(-6) M and 3.8 x 10(-6) M, respectively. The pA2 value and the IC50 value of terodiline for rat urinary bladder were 6.08 and 6.6 x 10(-6) M, respectively. In contrast, the pA2 value and the IC50 value of oxybutynin for rat urinary bladder were 7.69 and 4.5 x 10(-6) M, respectively, suggesting that oxybutynin exerts an anti-muscarinic effect at doses at which no discernible anti-KCl effect was observed, whereas propiverine and terodiline exerted both effects at the same doses. The inhibitory effect of drugs on the contraction induced by electrical field stimulation was tested. At a dose of 10(-7) g/ml, tetrodotoxin inhibited the contraction of rat and dog urinary bladder by 76.6% and 92.6%, respectively. Propiverine and verapamil dose-dependently inhibited the contractile response induced by electrical field stimulation at doses of 10(-5) M or more and 3 x 10(-6) M or more, respectively. At these concentrations, a marked anti-KCl effect of the drugs on smooth muscle was observed. On the other hand, atropine caused no inhibition of the contractile response in rat urinary bladder at a dose of 3 x 10(-5) M, and it inhibited the contraction in dog urinary bladder by 14.9% at a dose of 10(-5) M. These findings suggest that although propiverine exhibits both anti-muscarinic and anti-KCl effects in isolated rat and dog urinary bladder, the inhibitory effects of propiverine on the atropine-resistant part of contraction may be mainly due to its anti-KCl effect.

Acetylcholine↗

PubMed1999

The novel analgesic compound OT-7100 (5-n-butyl-7-(3,4,5-trimethoxybenzoylamino)pyrazolo[1,5-a]pyrimid ine) attenuates mechanical nociceptive responses in animal models of acute and peripheral neuropathic hyperalgesia.

We investigated the effects of OT-7100, a novel analgesic compound (5-n-butyl-7-(3,4,5-trimethoxybenzoylamino)pyrazolo[1,5-a]pyrimidi ne), on prostaglandin E2 biosynthesis in vitro, acute hyperalgesia induced by yeast and substance P in rats and hyperalgesia in rats with a chronic constriction injury to the sciatic nerve (Bennett model), which is a model for peripheral neuropathic pain. OT-7100 did not inhibit prostaglandin E2 biosynthesis at 10(-8)-10(-4) M. Single oral doses of 3 and 10 mg/kg OT-7100 were effective on the hyperalgesia induced by yeast. Single oral doses of 0.1, 0.3, 1 and 3 mg/kg OT-7100 were effective on the hyperalgesia induced by substance P in which indomethacin had no effect. Repeated oral administration of OT-7100 (10 and 30 mg/kg) was effective in normalizing the mechanical nociceptive threshold in the injured paw without affecting the nociceptive threshold in the uninjured paw in the Bennett model. Indomethacin had no effect in this model. While amitriptyline (10 and 30 mg/kg) and clonazepam (3 and 10 mg/kg) significantly normalized the nociceptive threshold in the injured paw, they also increased the nociceptive threshold in the uninjured paw. These results suggest that OT-7100 is a new type of analgesic with the effect of normalizing the nociceptive threshold in peripheral neuropathic hyperalgesia.

Amitriptyline↗

PubMed1999

Selective V2-receptor vasopressin antagonism decreases urinary aquaporin-2 excretion in patients with chronic heart failure.

Aquaporin-2 (AQP-2), a water channel located on the apical membrane of collecting duct cells, regulates water reabsorption under the control of vasopressin (AVP). Using an antibody directed to human AQP-2, a quantitative Western blot analysis was performed to determine the collecting duct responsiveness to an oral, nonpeptide, V2 receptor antagonist (VPA-985) in patients with chronic NYHA II and III heart failure. Standards were derived by conjugating the immunizing peptide to maleimide-activated bovine serum albumin and a standard curve was generated for each blot. Quantification of baseline steady-state AQP-2 excretion was done by collecting urine on the day before study drug administration. The next day patients received either placebo or VPA-985 at one of four different doses and urine was collected every 2 h. Thereafter, urinary AQP-2 excretion was calculated as a ratio of the urine flow and was expressed in pmol/h. During baseline, steady-state excretion did not change significantly (T0-T2, 458 +/- 44; T2-T4, 443 +/- 35; T4-T6, 422 +/- 35; T6-T8, 401 +/- 30). Compared to placebo, urinary AQP-2 excretion decreased significantly and in all groups in a dose-dependent manner during VPA-985 administration. The most impressive decrease was observed in the 250-mg group (T0-T2, 89 +/- 5; T2-T4, 50 +/- 18; T4-T6, 43 +/- 22; T6-T8, 42 +/- 23; P < 0.001 during each period compared with baseline and placebo results). VPA-985 significantly increased solute-free water clearance and urine output and significantly decreased urinary osmolality. Urinary AQP-2 excretion correlated best with solute-free water clearance during T0-T2 and T2-T4 collection, but a correlation with urinary osmolality and urinary output was also found during these periods. In conclusion, AQP-2 urinary excretion, as measured by quantitative Western analysis, is a sensitive biologic marker to assess the short-term responsiveness of the collecting duct to a V2 receptor AVP antagonist in chronic heart failure.

Administration, Oral↗

PubMed1999

[Current topics in the regulation of prostanoids--3. Prostanoid synthases and prostanoid receptors].

Formation of biologically active prostanoids from PGH2 occurs through a set of synthases for PGD, PGE, PGF, PGI and TXA2, following the cyclooxygenase reaction. Over the past few years, the genes of several prostanoid synthases have been cloned and the characteristics of the enzymes are now determined. In addition, receptors for prostanoids were also cloned and their structures were determined as G-protein coupled seven-transmembrane domain types belonging to the rhodopsin-type receptor superfamily. Based on these molecular biological findings, the mechanism of the diverse effects of prostanoids are being clarified. Selective inhibitors against the synthases and the selective agonists and antagonists for the prostanoid receptors are now being investigated rapidly for clinical application.

Animals↗

PubMed1999

[Current topics in the regulation of prostanoids--4. The feedback regulation by PPAR-gamma].

Recently, it has become known that lipophilic hormones such as steroids and thyroid hormones, or fat-soluble vitamins (vitamins A and D) pass through the cellular membrane and bind to the nuclear receptor superfamily to act as transcription factors. The metabolite of prostaglandin (PG) D2, 15-deoxy-D12,14PGJ2, has been identified as the ligand for peroxisome proliferator-activated receptor gamma (PPAR-gamma), a member of the nuclear receptor superfamily. It forms a transcription factor and is responsible not only for the differentiation of fibroblasts to adipocytes, but also for the regulation of activated macrophages. It is now known that thiazolidinediones and non-steroidal anti-inflammatory drugs classified as cyclooxygenase blockers such as indomethacine and ibuprofen also act as PPAR-gamma agonists and inhibit cytokine production from activated macrophages. PPAR-gamma has become recognized as a new therapeutic target for inflammation control.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed1999

[Efficacy of intra-arterial chemotherapy on life prolongation in patients with hepatic metastasis from colorectal cancer].

The efficacy of intra-arterial chemotherapy for life prolongation was investigated in patients with hepatic metastasis from colorectal cancer who visited our hospital from Jan. 1989-Mar. 1999, but without any other remote metastasis when the presence of their hepatic metastasis was detected. The subjects were assigned to 4 groups; group A (n = 8) was only treated by hepatectomy, group B (n = 27) by intra-arterial chemotherapy combined with hepatectomy, group C (n = 42) with intra-arterial chemotherapy alone, and group D (n = 23) by systemic chemotherapy through intra-venous or oral administration. The survival rates of these groups were determined, and the recurrence risk after hepatectomy was compared between group A and B. Further, the survival rate of the patients treated by intra-arterial chemotherapy was compared between the cases of PD and not-PD (including CR, PR, and NC). The median survival in cases of H1 and H2 was 405 days for group A, 1,018 days for group B and 245 days for group C, showing that group B had a significantly more favorable prognosis than either group A or group C. There were also significant differences in the median survival of H3 cases between group C (422 days) and group D (113 days). One-year cumulative recurrence risks in the residual livers of group A and group B were 79% and 28%, respectively. Thus, significant differences in the recurrence risk were found in the two groups. Meanwhile, the median survival of PD and non-PD cases was 240 and 588 days, respectively. These results suggested that local control by intra-arterial chemotherapy is useful for life prolongation.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1998

Upregulation of aquaporin 2 water channel expression in pregnant rats.

Water retention is characteristic of pregnancy but the mechanism(s) of the altered water metabolism has yet to be elucidated. The collecting duct water channel, aquaporin 2 (AQP2), plays a pivotal role in the renal water regulation, and we hypothesized that AQP2 expression could be modified during pregnancy. Sprague-Dawley female rats were studied on days 7 (P7), 14 (P14), and 20 (P20) of pregnancy, and expression of AQP2 in papillae was examined. Nonpregnant (NP) littermates were used as controls. Plasma osmolalities were significantly lower in pregnant rats by day 7 of gestation (P7 283.8+/-1.82, P14 284.3+/-1.64, P < 0.001, P20 282. 4+/-1.32, P < 0.0001, vs. NP 291.8+/-1.06 mosmol/kgH2O). However, plasma vasopressin concentrations in pregnant rats were not significantly different than in nonpregnant rats (NP 1.03+/-0.14, P7 1.11+/-0.21, P14 1.15+/-0.21, P20 1.36+/-0.24 pg/ml, NS). The mRNA of AQP2 was increased early during pregnancy: AQP2/beta actin: P7 196+/-17.9, P14 200+/-6.8, and P20 208+/-15.5%, P < 0.005 vs. NP (100+/-11.1%). AQP2 protein was also increased during pregnancy: AQP2 protein: P7 269+/-10.0, P14 251+/-12.0, P < 0.0001, and P20 250+/-13.6%, P < 0.001 vs. NP (100+/-12.5%). The effect of V2 vasopressin receptor antagonist, OPC-31260, was then investigated. AQP2 mRNA was suppressed significantly by OPC-31260 administration to P14 rats (AQP2/beta actin: P14 with OPC-31260 39.6+/-1.7%, P < 0.001 vs. P14 with vehicle) and was decreased to the same level of expression as NP rats receiving OPC-31260. Similar findings were found with the analysis of AQP2 protein. The decreased plasma osmolality of P14 rats was not modified by OPC-31260. The results of the study indicate that upregulation of AQP2 contributes to the water retention in pregnancy through a V2 receptor-mediated effect. In addition to vasopressin, other factors may be involved in this upregulation.

Actins↗