Promoting effects of phenobarbital on the enzyme-altered foci induced by intrahepatic gamma-ray-irradiation in the rat liver

Radiation-induced carcinogenesis of the rat liver using iridium-192 seeds as an intrahepatic radioactive source was studied by enzyme histochemical means. Rats were divided into six groups according to various combinations of one or two iridium-192 or stainless steel seeds and whether they were given a diet containing 0.05% phenobarbital (PB) or a basal diet (BD). Each group were sacrificed at 20, 40, and 60 weeks after intrahepatic insertion of the iridium-192 or stainless steel seeds. gamma-Glutamyl transpeptidase (GGT), glucose-6-phosphatase (G6Pase), and adenosine triphosphatase (ATPase) were stained in the liver tissues, and GGT-positive foci were quantified. Liver neoplasm was not evident, but enzyme-altered foci (EAF) were induced by gamma-ray irradiation. At every point (20, 40, and 60 weeks) after the insertion of the seeds, the GGT-positive area was larger in the rats given than those given BD. Moreover, despite the iridium-192 radioactivity decay, EAF developed continuously in the rats given PB, and persisted in those given BD from 40 to 60 weeks after insertion. These results indicated that phenobarbital promotes the development of EAF initiated by irradiation, as it promotes the process of chemical carcinogenesis in the rat liver.

Flow cytometric analysis of DNA synthetic phase fraction of the normal appearing colonic mucosa in patients with colorectal neoplasms

DNA synthetic (S) phase fractions of normal appearing colonic mucosa in Japanese and British patients with colorectal neoplasms were compared with those in patients without colonic neoplasms. Normal crypts were isolated from fresh surgical specimens of the large intestine by the use of EDTA. After fixation with 70% ethanol, isolated crypts were digested with pepsin into single nuclei suspensions. These were stained with propidium iodide and examined by flow cytometry. S phase fraction was calculated from the flow cytometry DNA histogram using Baisch's method. S phase fractions of normal appearing crypts in Japanese and British patients with colorectal tumours were not significantly different and analysed together. S phase fraction of normal appearing colonic crypts in 14 patients with familial adenomatous polyposis (FAP) was 10.23 (2.59%) (mean SD)) ranging from 5.8 to 18.8. S phase fraction of background normal mucosal in patients with large adenomas (over 2 cm) and adenocarcinomas were 9.74 (3.76%) (range, 2.7-16.1) and 8.93 (3.54%) (range, 2.9-18.9) respectively. In normal mucosa of patients without any colorectal neoplasms, S phase fraction was 8.99 (3.94)% (range, 3.9-17.7). There was no statistically significant difference in S phase fractions of normal mucosa in the four groups. Our results show that an increase in proliferative activity of background colonic crypts is not necessary for tumour development.

Poorly differentiated ('insular') carcinoma of the thyroid

Three cases of unusual poorly differentiated ('insular') carcinoma of the thyroid gland are presented. These three thyroid carcinomas were large; the tumors from patients 1 and 3 were encapsulated, and that from patient 2 showed invasive growth. Microscopically the tumors were characterized by well-defined solid nests (insulae), which were composed of rather small and uniform tumor cells with round to oval nuclei. Formation of small and colloid-containing follicles was associated with these nests to varying degrees. The tumors of patients 1 and 3 were composed entirely of insular components, but that of patient 2 was associated with small areas of well-differentiated follicular carcinoma. The metastatic tumors of patients 1 and 2 were essentially similar to the primary with small foci of follicular carcinoma. Patient 1 is alive with local and mediastinal node recurrences, but patient 2 died of the disease with local recurrences and metastases to lungs, bones and skin. Patient 3 had no recurrences and died of unrelated disease 5 years after surgery. The present study indicates that insular carcinomas have characteristic histologic features and a less favorable prognosis, confirming the findings of previous studies.

Spatial learning impairment in aged rats: comparing between aged basal forebrain lesioned and normal aged rats

Normal aged rats (26 months) displayed significant impairments in learning the Morris water maze task as compared with young adult rats (3 months). The learning deficits of aged basal forebrain (BF)-lesioned rats (26 months; ethylcholine aziridinium ion was injected into the bilateral basal forebrain at 3 months age) were more severe than those of normal aged rats. Choline acetyltransferase (ChAT) in the frontal cortex of aged BF-lesioned rats activity was significantly reduced, but not in normal aged rats which level was almost the same as that in young adult rats. Histological examination showed that cholinergic fibers (acetylcholinesterase staining) in the frontal cortex reduced in aged BF-lesioned rats, but not in normal aged rats. The number of binding sites (Bmax) for [3H]vesamicol, a ligand for the vesicular acetylcholine transporter, in the frontal cortex of normal aged rats was significantly less than that in young adult rats, while the Bmax of aged BF-lesioned rats was higher than that of normal aged rats. The levels of monoamines and their metabolites in the frontal cortex and striatum but not hippocampus of aged BF-lesioned rats were markedly reduced as compared with those of normal aged and young adult rats. These results taken together indicate that normal aged and aged BF-lesioned rats exhibit learning deficits and that the differences of the severity of spatial learning deficits between normal aged and aged BF-lesioned rats may be due to, at least in part, the different properties of cathecolaminergic, serotonergic and cholinergic dysfunctions in the discrete brain sites.

Antagonizing effects of VA-045 on reduced activity of rat locus coeruleus neurons following head injury or intravenous injection of clonidine

Based on the finding that VA-045, a novel apovincaminic acid derivative, had improved disturbance in consciousness, we examined the effects of the drug on the electrical activity of locus coeruleus (LC) neurons in animal models of consciousness disturbance. The animal models of consciousness disturbance used in this experiment were closed head injury (CHI) and intravenous injection of clonidine. CHI as well as clonidine injection reduced the spontaneous activity of LC neurons. The reduction of the spontaneus activity of LC neurons following CHI or clonidine injection was restored by intravenous injection of VA-045. The change of LC neuronal activity induced VA-045 preceded desynchronization of EEG. These results suggest that VA-045 exerts its ameliorating effect on consciousness disturbances, at least in part, by augmenting the spontaneous activity of noradrenergic LC neurons.

[Age-related changes in amplitude ratio, duration ratio and area ratio in nerve conduction studies]

We investigated the effect of aging on nerve conduction parameters in 184 subjects (aged 10-75 years) without any history or signs of peripheral neuropathy, in order to clarify the diagnostic parameters of demyelinating neuropathies in the aged. The CMAP amplitude ratio (proximal CMAP/distal CMAP), duration ratio and area ratio remained unchanged throughout the second to eighth decades. The lower limits of normal CMAP amplitude ratio (mean -3SD) were 0.79 (median nerve), 0.74 (ulnar nerve), 0.59 (peroneal nerve), and 0.48 (tibial nerve). The upper limits of normal CMAP duration ratio (mean 11+ 3SD) were 1.22 (median nerve), 1.19 (ulnar nerve), 1.35 (peroneal nerve), and 1.32 (tibial nerve). The lower limits of normal CMAP area ratio (mean -3SD) were 0.84 (median nerve), 0.78 (ulnar nerve), 0.61 (peroneal nerve), and 0.62 (tibial nerve). There were no age-related changes in amplitude ratio or duration ratio of SNAP, although the standard deviations increased with age. Since the amplitude ratio, duration ratio and area ratio are simple and age-independent, they can provide useful and reliable information for routine nerve conduction studies for aged patients with demyelinating neuropathies.

Optic neuritis in cerebral toxocariasis

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[Primary adenocarcinoma of the tunica vaginalis testis expressing CA19-9 antigen]

A 47-year-old man presented with a 10-year history of left scrotal swelling. No solid mass detected on sonogram, dark-red colored fluid aspirated, equivocal cytology, and elevated serum CA19-9 level prompted surgical exploration. Frozen section reported no malignancy of thickening of the tunica vaginalis. The final pathology adenocarcinoma, however, necessitated left radical orchiectomy and hemiscrotal resection, demonstrating no malignancy at the left testis nor epididymis. CA19-9 level was high (104,200 U/ml) in the fluid obtained at the first surgery and the tumor cells were positively stained for CA19-9. Imaging study including abdominal CT scan and upper G-I series and normalization of CA19-9 level denied other tumor existing. In conclusion, this is to our knowledge the first case report of adenocarcinoma of the tunica vaginalis expressing CA19-9 antigen.

Oncologic and cosmetic outcome in patients with breast cancer treated with wide excision, transposition of adipose tissue with latissimus dorsi muscle, and axillary dissection followed by radiotherapy

We evaluated the oncologic and cosmetic outcome in patients with breast cancer treated with wide excision, transposition of adipose tissue with latissimus dorsi muscle (LDM), and axillary dissection followed by radiotherapy. In this study, a wide excision of breast tissue was performed to obtain tumor-free margins. The subsequent breast deformity was not corrected in six patients in the early phase of the study (Group 1), and in 16 patients in the late phase (Group 2) in which the breast deformity was not remarkable at the time of operation. Breast deformity was corrected by transposing adipose tissue with LDM on a vascular pedicle in the remaining 51 patients (Group 3). Five year survival was 100%. Two patients developed distant metastases. None were found to have local recurrence. Fifty percent of the Group 1 patients, 69% of the Group 2 patients, and 67% of the Group 3 patients had an excellent or good cosmetic result. However, when the cosmetic results were evaluated in patients who underwent transposition and had small breasts, the results were excellent or good in 76%, compared to 38% in the patients who had reconstructions who had large breasts. The difference was statistically significant (p = 0.0309). Therefore, it was confirmed that wide excision and axillary dissection followed by breast radiation could provide adequate local control, but frequently resulted in breast deformity. However, transposition of adipose tissue may be useful to correct the breast deformity, especially in women with small breasts.

A case with quadruple primary cancers of head and neck

Despite progress in techniques for early detection and treatment of cancers, cases of multiple primary cancers are apparently increasing. This paper reported quadruple primary cancers of stomach, lung, hypopharynx and maxillary sinus in a 63-year-old male. He finally died of brain metastasis and pneumonia by MRSA (Me Resistant S. aureus).

Enhanced replication of orbiviruses in bovine testicle cells infected with bovine viral diarrhoea virus

Bovine testicle (BT) cells infected with non-cytopathogenic (NCP) bovine viral diarrhoea virus (BVDV) developed cytopathogenic effect (CPE) after superinfection with 7 Orbiviruses, whereas no CPE was induced by them in the absence of NCP BVDV infection. The CPE was accompanied by the enhanced replication of Orbiviruses. Seven of 10 strains of NCP BVDV induced the enhanced replication of Ibaraki virus, a member of Orbivirus. These 7 strains of NCP BVDV were END phenomenon positive. In contrast, the absence of CPE and the suppression of growth of Ibaraki virus were seen in BT cells infected with the other 3 strains which were END phenomenon negative. The END phenomenon negative viruses were different markedly from the END phenomenon positive viruses with respect to interactions with Orbivirus. The mechanism of the enhanced replication of Orbivirus seems to be explained with the suppression by the END phenomenon positive NCP BVDV to the interferon production of Orbivirus in BT cells.

Intrasellar neuronal choristoma associated with growth hormone-producing pituitary adenoma containing amyloid deposits

The histological, immunocytochemical, and ultrastructural features of an intrasellar neuronal choristoma associated with pituitary growth hormone (GH)-producing adenoma are reported. Immunohistochemistry studies and electron microscopy examination showed the adenoma cells to be positive for GH but negative for prolactin, and the neurons of the choristoma to have GH-releasing factor (GRF) neurosecretory activity. The adenoma also had many amyloid deposits in its extracellular space immunoreactive to GRF. This is the first report of the tumor containing amyloid deposits.

Esophagocardioplasty for achalasia in closure of a complicated esophagobronchial fistula

We report a rare case of benign esophagobronchial fistula associated with achalasia. The fistula healed spontaneously after esophagocardioplasty with a gastric patch, suggesting the utility of this procedure.

NAD(+)-glycohydrolase from Streptococcus pyogenes shows cyclic ADP-ribose forming activity

NAD(+)-glycohydrolase from Streptococcus pyogenes was purified by successive chromatography on CM Sepharose CL-6B, Sephacryl S-200 HR and hydroxyapatite. The purified enzyme possessed synthesis and hydrolysis activities of cyclic ADP-ribose (cADPR), a newly found second messenger for Ca2+ mobilisation, along with cleavage activity of the ribose-nicotinamide bond in NAD+.

A long-lasting change in the excitability of fetal brain neurons following activation of dam's hypothalamus in rats

The influence of the dam's brain on the electrical activity of brain neurons was examined in the rat fetus while the fetus was still connected to the dam by the umbilical cord. Under urethan anesthesia, the spontaneous or glutamate-induced discharge of single brain stem neurons in fetuses was decreased by electrical stimulation of the dam's hypothalamus (Hyp). The changes occurred 21-122 s after start of the stimulation and persisted throughout the recording until the cells were lost after 2.4-9.5 min. The effects of electrical stimulation of dam's midbrain reticular formation (MRF) were much weaker and of shorter duration compared with Hyp stimulation. The dam's blood pressure was increased immediately after the beginning of MRF or Hyp stimulation. The change was always greater with MRF than with Hyp stimulation. Activation of the dam's MRF and Hyp had no marked influence on the blood flow in the fetal brain. These results indicate the presence of a functional interaction between the brain of the dam and that of its fetus mediated through the placenta.

[A case of portal-systemic encephalopathy with slowly progressive, non-flapping tremor]

A 52-year-old man has slowly developed a non-flapping tremor during 30 years. He also had suffered from poor concentration for two years. He had, however, no history of episodic disturbance of consciousness. He had no other neurological symptoms except for tremor and hyperreflexia. The tremor was postural and intentional, and extremely increased at the end point. The factor of intentional tremor and hyperkinesia volitionnelle seems to be present in the tremor. Laboratory examination disclosed a hyperammonemia, reduction in Fisher ratio, and poor excretion of ICG. Selective abdominal angiography visualized a large shunt vessel between the left gastric vein and the left renal vein. The normal liver scintigram with 99mTc excluded the dysfunction of liver, and we conclude that the shunt vessel might be congenital. Tremor markedly improved after normalizing blood ammonia level by resection of the shunt vessel. The present case suggests that tremor, even without episodic disturbance of consciousness, could be based on the portal-systemic encephalopathy.

Endothelium-dependent contraction in intrapulmonary arteries: mediation by endothelial NK1 receptors and TXA2

1. We have examined whether three natural tachykinins, substance P (SP), neurokinin A (NKA) and neurokinin B (NKB) induce an endothelium-dependent contraction (EDC) in the rabbit isolated intrapulmonary artery. 2. Removal of the endothelium almost abolished the contraction induced by SP (10(-8) M) while it did not attenuate the contraction induced by SP (10(-7) M), NKA (10(-9) - 10(-7) M) or NKB (10(-8) and 10(-7) M). 3. The EDC induced by SP (10(-8) M) was abolished by NK1 antagonists (FK-888, CP-96345, CP-99994 and SR-140333) but not by an NK2 antagonist (SR-48968). 4. The EDC induced by SP was attenuated by cyclo-oxygenase inhibitors (aspirin and indomethacin), thromboxane A2 (TXA2) synthetase inhibitors (OKY-046, KY-234 and KY-063) and a TXA2 antagonist (S-1452). 5. The rank order of potency causing endothelium-independent contraction (EIC) was NKA > NKB > SP. The EIC induced by SP (10(-7) M) was attenuated by an NK2 antagonist but not by NK1 antagonists, cyclo-oxygenase inhibitors, TXA2 synthetase inhibitors or a TXA2 antagonist. 6. In conclusion, SP at 10(-8) M induces EDC via endothelial NK1 receptors and TXA2 production, and SP at 10(-7) M induces EIC via NK2 receptors in the rabbit intrapulmonary artery.

Effects of basic fibroblast growth factor on proliferation, the expression of osteonectin (SPARC) and alkaline phosphatase, and calcification in cultures of human pulp cells

Basic fibroblast growth factor (bFGF) may be involved in the development and repair of dentine and pulp because bFGF, its related peptides, and FGF receptors are expressed in dental mesenchymal cells. In this study, we examined the effects of bFGF on DNA synthesis, osteonectin/SPARC levels, alkaline phosphatase (ALPase) activity, their mRNA levels, and calcium levels in cultures of human pulp cells. Pulp cells were isolated from three healthy upper wisdom teeth of three patients and maintained separately. These cells produced SPARC, ALPase, and calcified nodules and there was a close correlation between the SPARC-synthetic activity of the cell lines and their levels of ALPase and calcification. The levels of SPARC, ALPase and calcium deposits in the three pulp cell cultures were 10-250 times those of human foreskin fibroblasts. Western blots showed that the pulp cells produced 38-kDa SPARC. Northern blots showed that the pulp cells expressed flg (FGF receptor type 1) transcripts throughout all culture stages, irrespective of the presence or absence of bFGF. The addition of bFGF to the pulp cultures suppressed the increases in ALPase activity, SPARC synthesis, and their mRNA levels, although it increased the incorporation of [3H]thymidine into DNA > 10-fold. The effects of bFGF on ALPase activity and SPARC synthesis were reversible. Furthermore, bFGF abolished the calcification of the extracellular matrix; the calcium content of bFGF-free cultures. These findings suggest that bFGF is a potent mitogen for human pulp cells and that it inhibits the expression of the odontoblast phenotype by the cells at least partly at pretranslational levels.

Effects of the novel water-soluble calcium antagonist (+/-)-3-(4-allyl-1-piperazinyl)-2,2-dimethylpropyl methyl 1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylate dihydrochloride on the responses of isolated canine arteries

The effects of NKY-722 ((+/-)-3-(4-allyl-1-piperazinyl)-2,2-dimethylpropyl methyl 1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylate dihydrochloride, CAS 117241-46-0), a new water soluble dihydropyridine derivative on the responses of isolated canine arteries were examined. NKY-722 (IC50: 5-16 x 10(-10) mol/l), nicardipine (IC50: 5-10 x 10(-10) mol/l) and nifedipine (IC50: 44-195 x 10(-10) mol/l) relaxed four arteries in the potency order of basilar > coronary > mesenteric > intrarenal arteries. NKY-722 was nearly equipotent to nicardipine and about 10 times more potent than nifedipine. [3H]NKY-722 was accumulated in the four arteries in the same order of amount as the vasoinhibitory effect. All three drugs inhibited the contraction induced by Ca2+ and methyl 1,4-dihydro-2,6-dimethyl-3-nitro-4-(2-trifluoromethylophenyl)-p yri dine-5- carboxylate (Bay K 8644) in the mesenteric arteries, indicating their Ca2+ antagonistic actions. NKY-722 and nicardipine were nearly equipotent and about 100 times more potent than nifedipine on the Ca(2+)-induced contraction and was about 4 times more potent than nicardipine and 400 times more potent than nifedipine on the Bay K 8644-induced contraction. NKY-722, nicardipine and nifedipine relaxed the mesenteric arteries precontracted with KCl by more than 90%, while they relaxed the arteries contracted with PGF2 alpha, 9,11-dideoxy-9 alpha, 11 alpha-methanoepoxy-PGF2 alpha (U-46619) and endothelin-1 only by 40-70%. The IC50 values of NKY-722 and nicardipine were similar and much smaller than that of nifedipine for all four contracting agents.(ABSTRACT TRUNCATED AT 250 WORDS)

[Experimental study on early detection of alloxan-induced pulmonary injury by magnetic resonance imaging]

We studied the early detection of alloxan-induced pulmonary injury by magnetic resonance imaging in vivo. Permeability edema was induced in ten rats by intravenous injection of alloxan at 100 mg/kg. T1-and T2-weighted images were acquired in five rats every 30 min for 120 min after alloxan injection. Five rats served as controls. The rats were sacrificed immediately after imaging and examined microscopically. CT images were also acquired in five rats every 30 min for 120 min after alloxan injection. Five rats served as controls. The rats were sacrificed immediately after imaging, and the wet-to-dry ratio of the lung was measured. In T1-weighted images, relative signal intensity from the lung with permeability edema rose from 30 min to 120 min, and was greater than that from normal lung every time. In T2-weighted images, there was no statistically significant difference in relative signal intensity of the lung between permeability edema and the control during 120 min. In CT images, there was also no statistically significant difference in lung density between permeability edema and the control during 120 min. There was no statistically significant difference in the wet-to-dry lung ratio between edematous lung and normal lung. In histological study, mild congestion and interstitial edema were observed in edematous lung. These results suggest the potential capability of MR imaging in detecting the early phase of permeability pulmonary edema.

Prevalence of HTLV-I-associated uveitis in the Kanto Plain, Japan

BACKGROUND

Seroprevalence of antibody to human T-lymphotropic virus type I (HTLV-I) is high in the island of Kyushu, Japan. Reports on the etiological analysis of HTLV-I in patients with uveitis primarily document cases in this island. We studied the seroprevalence of HTLV-I at the Department of Ophthalmology in Yokohama City University Hospital and in Odawara Municipal Hospital, which are in the Kanto Plain on the island of Honshu, Japan.

METHODS

The subjects were 741 patients who visited the two hospitals. The presence of serum antibodies against HTLV-I was assessed using the method of particle agglutination.

RESULTS

Of 454 patients with nonuveitic ocular diseases, 9 (1.98%) were seropositive. Of 143 patients with definite diagnosis of uveitis, 1 (0.70%) was seropositive. Of 144 patients with non-specific uveitis (etiology undefined), 8 (5.56%) were seropositive. Thus, the prevalence of serum antibodies to HTLV-I was higher in patients with non-specific uveitis than in patients with specific uveitis or nonuveitic ocular diseases. Common ocular symptoms of 8 HTLV-I-infected patients with non-specific uveitis were compatible with the clinical features of uveitis described as HTLV-I-associated uveitis (HAU).

CONCLUSION

It is important to suspect HAU in patients with uveitis of unknown etiology, even outside known areas of prevalence.

Expression of p53 and flow cytometric DNA analysis of isolated neoplastic glands of the stomach: an application of the gland isolation method

The expression of p53 was studied immunohistochemically in combination with the DNA ploidy pattern by gland isolation in 97 alcohol-fixed gastric lesions. A polyclonal antibody, CM-1, was applied to the paraffin-embedded sections in this study. Overexpression of the p53 protein was found in 73.2% of 41 well or moderately differentiated gastric carcinomas and 52.2% of 23 cases with poor differentiation (P < 0.05). Immunoreactivity of p53 was also detected in isolated cancerous glands. No p53 immunoreactivity was detected in benign gastric lesions including adenomas, hyperplastic polyps and regions of intestinal metaplasia. In addition, flow cytometric DNA analysis was performed on isolated glandular epithelium adjacent to the portions used for immunostaining. DNA aneuploidy (DA) was detected in 85.7% of the well or moderately differentiated carcinomas and 42.9% of those with poor differentiation (P < 0.05). There was a positive correlation between DA, p53 positivity and the presence of regional lymph node metastasis, but not with other clinicopathological variables. In spite of the limited applicability of this method to poorly differentiated gastric cancer, we found that immunostaining and flow cytometry in combination with the gland isolation method facilitates analysis of gastric carcinogenesis.

[Secondary myeloid/natural killer cell acute leukemia appeared in multiple myeloma treated with melphalan]

A 67-year-old woman was treated with MP-P therapy and combination chemotherapy for multiple myeloma IgG-lambda type. After the therapy for about three years, pancytopenia developed. Bone marrow aspiration study revealed a few of myeloma cell and many atypical cells showing promyelocytic feature. Chromosomal abnormality was 46, X, -X, +8, -13, +mar. CD33 and CD56 were positive, but CD16 and HLA-DR were negative. We diagnosed as multiple myeloma complicated with secondary myeloid/natural killer (NK) cell acute leukemia. After she had been treated with low dose etoposide for leukemia, she obtained complete remission. But since myeloma progressed and the amount of M protein was increased, she was treated with dexamethasone and low dose etoposide, resulting in a decrease in the amount of M protein. After that, because of leukemic cell re-proliferation, she was treated with etoposide. However, she died of sepsis due to severe myelosuppression. This case was interesting one in coexist of multiple myeloma and secondary myeloid/NK cell acute leukemia, and those affecting her clinical course each other.

Effect of loratadine on immediate and delayed type hypersensitivity reactions

Loratadine (CAS 79794-75-5) was effective in inhibiting the contractions of the ileum induced by histamine in guinea pigs. The drug also caused an anti-acetylcholine, anti-serotonin and anti-leukotriene D4 (LTD4) effect. In addition, loratadine inhibited the synthesis of leukotrienes more potently than ketotifen. On the other hand, in in vitro studies of histamine release from rat peritoneal mast cells induced by compound 48/80 or lung fragments in actively sensitized guinea, pigs, loratadine elicited a significant inhibition at a concentration of 5 mumol/l. In ex vivo studies, the drug inhibited histamine release from lung fragments induced by concanavalin A, and significant effect lasted for 24 h when the drug was administered at a dose of 20 mg/kg. The drug inhibited LTD4 release as well as histamine from lung fragments in actively sensitized guinea pigs. Loratadine inhibited not only 45Ca uptake into the rat peritoneal mast cells but also Ca2+ release from the intracellular Ca store induced by compound 48/80 or A23187. Loratadine increased cAMP content in rat lung preparation while decreasing cGMP content. Loratadine caused no significant change in order parameter and phospholipase A2 activity. The drug was more potent than ketotifen and terfenadine in inhibiting antigen-induced increase in airway resistance in guinea pigs. In addition, the effect of loratadine on airway resistance was sustained for 12 h. Loratadine inhibited an increase in dye leakage into the nasal cavity in rats.(ABSTRACT TRUNCATED AT 250 WORDS)