Haruko Koizumi

Species differences in vacuolation of the choroid plexus induced by the piperidine-ring drug disobutamide in the rat, dog, and monkey.

A subchronic oral toxicity study of disobutamide, a piperidine ring compound with antiarrhythmic activity, was conducted at doses of 30, 100, and 250 mg/kg in rats, 45 mg/kg in dogs, and 90 mg/kg in monkeys. Numerous vacuoles were observed in various organs such as the liver, kidneys, heart, lungs, spleen, thymus, stomach, and choroid plexus in these animals. The epithelium of the choroid plexus (CP), however, showed severe vacuolation in rats and monkeys but not in dogs. The vacuoles corresponded to enlarged and myelin-figured lysosomes observed by electron microscopy, revealing morphological characteristics which have been reported as drug-induced phospholipidosis. In a further study, the drug penetration to cerebrospinal fluid (CSF) and the drug concentration in CP were examined in these animals. Daily po doses of 250, 45, and 90 mg/kg were, respectively, administered to rats, dogs, and monkeys to maintain approximate equivalency in peak blood concentrations across species, over a course of 35 days. The concentration of the drug in the CP was higher in rats and monkeys than in dogs, and the CSF/serum ratio of the drug concentration was extremely high in rats. The uptake of the drug by the CP in vitro was high in rats, monkeys, and dogs, in this order. In dogs, both direct contact of the drug with the CP during incubation and intraventricular administration induced vacuolation in the epithelium. From these results it was concluded that differences of the drugs penetration into the CSF and its uptake by the choroid plexus epithelium are responsible for the species differences of CP vacuolation in the animals.

Studies on the validity of urinary enzyme assay in the diagnosis of drug-induced renal lesions in rats

The validity of urinary enzyme assays in the diagnosis of renal lesions was studied in rats for evaluation in comparison with other tests such as urinalysis and serum biochemical assay. Tubular damages of slight or severe degree were induced by daily intramuscular administration of 500 mg/kg or 1,000 mg/kg of kanamycin (KM) for 7 and 6 days respectively. Glomerular lesions were induced subcutaneous injection of 30 mg/kg of puromycin (PM) for 6 days. The enzymes, assayed daily before and after the onset of administration, were lactic dehydrogenase (LDH), aspartate aminotransferase (GOT), alkaline phosphatase (AI-P), acid phosphatase (Ac-P), leucin aminopeptidase (LAP) and γ-glutamyl transpeptidase (γ-GT). The distribution of these enzymic activities in the kidneys was histochemically examined. Assays of LDH and GOT on the kidney tissue homogenate were also conducted. Histological alterations of the kidneys were examined in the rats sacrificed after termination of administration. Significant elevation of the LDH and GOT urine levels were observed within 24 hours in rats treated with 500 mg/kg of KM with the high enzyme levels being maintained throughout the administration period, while the other enzymes remained within pretreatment levels or were only slightly elevated. Serum urea nitrogen (BUN) and creatinine levels remained unchanged with no abnormality being found in the urinalysis of this group. In the group treated with 1,000 mg/ kg of KM, concomitant rising of all urine enzyme levels was observed, with elevation of the LDH and GOT levels being extreme while the BUN and serum creatinine levels rose only at the termination of the administration period. The BUN level rose earlier than did most of the urinary enzymes in puromycin-treated rats. Depletion of LDH activity was histochemically demonstrated in the kidneys where no histological alteration was observable, while the activities of AI-P, γ-GT, and LAP showed no distinct changes until the tabular destruction became severe. Upon termination of both KM and PM administration, the depletion of LDH and GOT activities was noted in a kidney homogenate assay for the enzymes. These results clearly showed that among the enzymes studied, the LDH and GOT urine levels are the most sensitive indicators for detecting proximal tubular lesions induced by KM. It was further demonstrated that the urinary enzyme assay in combination with serum BUN measurement is an effective examination for distinguishing tubular from glomerular lesions.

In vivo Function of Homing Receptors Participating in Lymphocyte Recirculation: Transfer Analysis in SCID Mice

In order to examine the in vivo function of the adhesion molecules implicated in lymphocyte homing, blocking effects of antibodies against various adhesion molecules on lymphocyte migration were tested in SCID mice into which BALB/c donor splenocytes had been transferred. It was proved that the transferred donor splenocytes migrated to peripheral lymph nodes (LNs) of SCID mice. T and B lymphocytes were distributed in the specialized compartments as seen in the LNs of normal mice. Migration of lymphocytes to the local LNs was accelerated by stimulation with ovalbumin and complete Freunds adjuvant. This experimental system with accelerated migration was applied to analyze the in vivo function of adhesion molecules, and the following findings were obtained. Combined use of antibodies against lymphocyte-function-associated antigen 1 (LFA-1) and intercellular adhesion molecule 1 (ICAM-1) strongly inhibited the migration of T lymphocytes to the peripheral LNs. Antibodies against very late antigen 4 (VLA-4) and vascular cell adhesion molecule 1 (VCAM-1) led to diminished B lymphocyte migration and disturbed compartmentalization of T lymphocytes in the paracortex. Migration of both T and B lymphocytes to the LNs was completely inhibited by the antibody against L-selectin. These results indicate that L-selectin plays an essential role in migration of both T and B lymphocytes into peripheral LNs but LFA-1/ ICAM-1 and VLA-4/VCAM-1 play different roles in compartmentalization of T and B lymphocytes in the peripheral LNs. In contrast, these adhesion molecules were not involved in lymphocyte migration to the splenic white pulp, indicating that the mechanisms for lymphocyte homing to the white pulp are quite different from those to the peripheral LNs.