The maxillary regions of day-12.5 ICR mouse fetuses were cultured in a chemically-defined serumless medium and the effects of methylxanthine derivatives on cultured palates were studied. Explanted palates were treated for 72 hr in vitro with 0.5-2 mM caffeine (CA), 1-2 mM theophylline (TP), or 1-2 mM theobromine (TB). Although the three compounds tested did not prevent the contact of opposing palatal shelves, palatal fusion was inhibited by CA and TP at a concentration of 2 mM, and the inhibitory effect of CA was more evident than that of TP. On the other hand, TB did not exert an inhibitory effect on palatogenesis at 2 mM. Since the in vitro toxicity of the methylxanthine compounds appeared to correlate well with their in vivo teratogenic potential, the organ culture method of fetal rodent palates should be a useful tool for screening teratogenic agents, especially those causing cleft palate.
On the assumption of that the oral administration of an acid-unstable test compound into the empty stomach could enhance the systemic exposure to the test compound, the non-pregnant and pregnant rats had free access to the diet only for five hours per day. Female rats under the restricted feeding for a period of 21 days took diet at two thirds of the daily food-intake by the control animals, and lost their weight more than 10%. The vaginal smear test in these animals revealed a prolonged estrous cycle and diestrous period over four days. On the other hand, the restricted feeding from Day 0 to Day 17 of gestation suppressed the weight gain of pregnant animals but did not cause any significant influence upon the litter data, incidence of external anomalies or fetal skeletal development. The restricted feeding from Day 0 of gestation to Day 7 of lactation seriously disturbed the nursing behavior and the growth of offspring. These results suggested that the dosing method under the above-mentioned restricted feeding might be applicable to the teratology study but could not be applied to the fertility study nor to the peri- and post-natal study.
The modifying potential of diethylmaleate (DEM) and NH4Cl on promotion by butylated hydroxyanisole (BHA) or NaHCO3 of urinary bladder carcinogenesis in rats initiated with N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) was investigated. Six week old animals received 0.05% BBN for 4 weeks and then BHA(2%)+DEM(0.15%), BHA+NH4Cl(1%), NaHCO3(3%)+DEM, NaHCO3+NH4Cl, BHA, DEM, NH4Cl or no supplement, administered during experimental weeks 5-36. BHA and NaHCO3 clearly amplify the induction of papillary or nodular (PN) hyperplasias and papillomas in rats initiated with BBN. The promoting activity of BHA was not affected by simultaneous administration of DEM or NH4Cl. The enhancing effects of NaHCO3, in contrast, were clearly diminished by concurrent administration of either of these agents. DEM itself did not influence lesion development whereas NH4Cl reduced the incidence of papillomas. In a second experiment, rats exposed to the same protocol were killed at week 8, and assessed for levels of lipid peroxides in the bladder tissue. No remarkable alterations were observed in any group. Thus, the fact that DEM did exert inhibiting effects on tumor promotion by NaHCO3 without decreasing the urinary sodium ion concentration or pH and influence on lipidperoxide levels, suggests essential differences in the mechanisms of action of different types of bladder promoters.
The in vitro effect of 13 metal ions on the activity of erythrocyte pyrimidine 5'-nucleotidase (P5N) was investigated. Particular metals belonging to the boron group have recently been used as materials in a semi-conductor manufacturing. Of these metal ions, Ga exhibited no inhibition of erythrocyte P5N, while In extensively inhibited the erythrocyte P5N activity at concentrations of 10-4 to 10-3 M. In addition, the activity of erythrocyte P5N was inhibited by 90-96% when the metal ions such as Cu, Ag, Cd, Hg or Pb were added to the incubation mixture at concentrations of 10-4 to 10-3 M. On the other hand, there was no difference between sulfate and nitrate in the in vitro effect of the metal ions on the activity of erythrocyte P5N.
Phenobarbital (PB) was orally administered once at a dose of 100 mg/kg to the liver injury model rats treated with DL-ethionine (ET), and the effects of PB on the liver drug metabolizing enzymes (DME) were chiefly examined. Liver weight, liver microsomal protein content, liver aniline 4-hydroxylase (ANH) activity, and aminopyrine N-dimethylase (AMD) activity were markedly increased in the ET-treated rats receiving PB. These findings suggested the induction of DME in the liver. However, the induction pattern of each enzyme was different. AMD activity at 48 hr after dosing of PB in the ET-treated rats was increased in the same degree as that in the control (normal). Whereas, ANH activity at 48 hr after dosing in the ET-treated rats was higher than that in normal rats. Liver lactate dehydrogenase (LDH) activity at 48 hr after dosing in the ET-treated rats was markedly increased, but such induction was not seen in normal rats. These findings indicates that DME in the liver is induced by PB treatment in the ET-treated rats as well as in normal rats, and that the ET-treated rats have a function of physiological adaptation similar to that in normal rats. The induction pattern of liver or serum enzymes in the ET-treated rats receiving PB was different from that in normal rats. Furthermore, the induction pattern of these enzymes in the ET-treated rats receiving PB was different from that in the normal rats, which may be attributed to the difference of localization in liver cells of these enzymes affected by PB.
The hypertensive effect on the development of the prostatic abnormality in spontaneously hypertensive rats (SHRs) was examined using Efonidipine hydrochloride, a calcium antagonist. The control SHRs were given a high sodium and potassium diet (SP-diet) alone, and the treated SHRs were given a SP-diet with 0.15% Efonidipine hydrochloride from 8 to 28 weeks of age. The systolic blood pressure (SBP) in the control SHRs increased with age, while the elevation of SBP was significantly prevented in the treated SHRs. Light-microscopically, the prostatic lesion was observed both in the control and treated SHRs. The glandular lumen was narrowed with papillary protrusions, and the epithelium was composed of tall columnar epithelial cells. However, hypertension-induced complications in kidneys and hearts were not observed in the treated SHRs. These results suggested that the prostatic abnormality of SHRs might not be the consequent lesions upon hypertension.
To clarify the profile of the tacrolimus (FK506)-induced nephrotoxicity and its mechanism, 1, 2 and 4 mg/kg/day of tacrolimus was administered intramuscularly (i.m.) to spontaneous hypertensive rats (SHR) for 2 weeks, and biochemical and pathological parameters were studied in the animals. The acute nephrotoxicity of tacrolimus was characterized as increase of blood urea nitrogen (BUN) and plasma creatinine (P-Cr) levels in the groups of 1 mg/kg/day and more, decrease of creatinine clearance (CCr) value in the groups of 2 mg/kg/day and more, and histopathologically luminal narrowing of the arteriole adjacent the glomerulus in the groups of 1 mg/kg/day and more. These changes were associated with an increase of plasma renin activity (PRA) and urinary thromboxane B2 content and decrease of 6-keto-prostagrandinF1α (6-keto-PGF1α) content. Nilvadipine, which is one of the Ca2+ antagonist and is known to have renal vasodilating activity, prevented both biochemical and histopathological changes due to tacrolimus. The results indicated that the acute nephrotoxicity of tacrolimus was derived from impairment of glomerular function associated with the constriction of the renal arteriole brought about by the drug. All of these renal disorders induced by tacrolimus recovered completely or partially when the drug was withdrawn for 2 or 4 weeks. Consequently, the acute nephrotoxicity of tacrolimus in SHR was considered to be reversible.
To examine changes in serum TSH and determine whether the sustained excess is necessary for the development and/or progression of thyroid tumors, male F344 rats were administered drinking water containing thiourea (TU), at 0.1 or 0.05%, or sulfadimethoxine (SM), at 0.025 or 0.0125%, for one week in Experiment I. All of the treated animals showed decreased serum levels of T3 and T4 and increased TSH. In Experiment II, male rats were given a s.c. injection of N-bis(2-hydroxypropyl) nitrosamine (DHPN:1500 mg/kg BW) and, starting one week later, received drinking water containing the same doses of TU or SM as in Experiment I for the following 20 weeks. Thyroid follicular proliferative lesions were induced in most rats treated with TU and SM. However, these treated animals did not demonstrate any consistent alterations in serum T3, T4 and TSH levels, except for the high dose TU group. The present studies thus suggest that thyroid tumors can grow even under conditions of fluctuating serum TSH levels during the progression phase, although TSH stimulation might be an absolute requirement in the early phase of tumor development.
In order to clarify which species of cytochrome P-450 is involved in activation of benzo(a)pyrene (BP) in untreated rat liver, strain and sex differences in the ability of rat liver 9000 g supernatant (S-9) to mutagenically activate BP was investigated using Ames test. The numbers of histidine revertants in Ames test after pre-incubation of TA 98 strain of Salmonella typhimurium and BP with liver S-9 from male rats were markedly higher than those obtained using female rats. In addition, a marked strain difference (Wistar>DA) in the ability of liver S-9 from Wistar and DA rats to activate BP was observed. Antibody against cytochrome P-450 2D inhibited up to 50% of the revertant formation by the activation of BP with liver S-9 from male Wistar rats. These results indicate the partial involvement of cytochrome P-450 2D subfamily as well as cytochrome P-450 species specific to male rats in activation of BP to ultimate mutagen in untreated rat liver.