Research communications in chemical pathology and pharmacology最新文献

To elucidate the interaction between the renin-angiotensin system and arginine vasopressin (AVP), we investigated the change in the renal AVP receptor in the spontaneously hypertensive rat (SHR) treated with an angiotensin-converting enzyme (ACE) inhibitor, cilazapril. SHR (age 15 weeks) were given oral cilazapril 10 mg/kg body weight daily for 25 days (ACEI group). Systolic blood pressure was significantly decreased in the ACEI group as compared with the untreated SHRs (control group) after day 2. Urine volume in the ACEI group was 3- to 5-fold higher than that in the control group. Under these conditions, the renal AVP receptor was studied using the radiolabeled receptor assay (RRA) of [3H]-AVP from renal medulla membrane fractions. The serum concentrations of sodium, potassium, chloride, urea nitrogen and creatinine were not significantly different between the two groups. The plasma concentration of AVP in the ACEI group was higher than that in the control group. The dissociation constant (Kd) in the ACEI group was significantly lower than that in the control, although there was no significant change of maximum binding capacity (Bmax) between the two groups. We previously reported that the number of renal AVP receptors decreased in rats with diabetes insipidus which were treated with lithium, suggesting that the change in the AVP receptor is a primary cause of polyuric state induced by lithium. In the present study, the diuretic state and the decrease in blood pressure induced by cilazapril resulted in a marked decrease in the Kd of the renal AVP receptor and an increase in the plasma AVP level. It is suggested that plasma AVP and renal AVP receptors in SHR responded to the diuretic state induced by cilazapril by increasing the secretion and renal receptor affinity. We conclude that the AVP system plays an important role in the regulation of the fluid balance under diuretic conditions caused by ACE inhibitor treatment.

Stannous chloride (SnCl2) facilitates the calcium (Ca) entry into the frog motor nerve terminals. To compare the mode of action of SnCl2 on the Ca channels in the mouse with that in the frog, we investigated the effects of SnCl2 on the inward Ca current at the nerve terminals. SnCl2 (0.1 mM) did not change the second positive component of the action potential (an outward potassium (K) current) at the terminal part of the nerve terminal. SnCl2 (0.1 mM) increased the amplitude of the prolonged negative or positive deflection (an inward Ca current) evoked by treatment with 1 mM tetraethylammonium and 0.1 mM 3,4-diaminopyridine at the terminal or preterminal part of the nerve terminal, respectively. This augmenting effect of SnCl2 was inhibited by cumulative addition of Ca channel blockers, i.e., 0.1 mM CdCl2, 5 mM NiCl2, 5 mM CoCl2, 5 mM MnCl2, or 10 mM MgCl2. From the results obtained, it has been confirmed that SnCl2 facilitates the transmitter release by enhancing the Ca influx at the nerve terminals but not by blocking the K channels and that the mode of action of SnCl2 in the mouse is identical with that in the frog.

The activities (C3a, C4a, C5a) and concentrations (CH50, C3, C4, C5) of serum complement were measured to evaluate the involvement of complement in sepsis. We studied 27 patients with sepsis who were divided into the survivors (Group 1) and the nonsurvivors (Group 2). The levels of C3a, C4a, and C5a were all significantly higher in Group 2 than in Group 1 and closely reflected the severity of sepsis. Levels of C3 and C4 were significantly lower in Group 2 than in Group 1, presumably because these components were consumed as a result of activation of both the alternative and classical pathways. The levels of CH50 and C5 did not differ significantly between the two groups. These findings suggest that complement is closely involved in the exacerbation of the condition of septic patients, and that the measurement of complement activity is useful for evaluating the severity of sepsis.

Myo-inositol-1,4,5-triphosphoric acid (IP3) formation stimulated by (+-)-1-amino-1,3-cyclopentane-trans-dicarboxylic acid (trans-ACPD) was examined in the cortex, hippocampus and cerebellum of iron-induced epileptic rats and epileptic El mice. Increased IP3 formation by trans-ACPD was observed in the cortex, hippocampus and cerebellum of iron-injected rats while it was found in the hippocampus and cerebellum of the saline-injected control rats. Increased IP3 formation by trans-ACPD was remarkably higher in the hippocampus of iron-injected rats than the other regions. Increased IP3 formation by trans-ACPD was observed in the cortex, hippocampus and cerebellum of ddY mice, while such an increase was found only in the cerebral cortex and not in the hippocampus and cerebellum of El mice. These findings suggest that the inositol response may be involved in the seizure mechanisms of iron-induced epileptic rats and epileptic El mice in some different forms.

Oral administration of crude extracts of Trionyx carapax into rats was found to protect the liver from its CCl4-induced injury as judged by morphological and biochemical observations. The active principle was purified from crude extracts of Trionyx carapax by Sephadex G-75, Sephadex G-25, DEAE-cellulose and silica gel column chromatographies. The results of elemental analysis, infrared and mass spectroscopy demonstrated the purified component to be identical to uracil. Upon administration, authentic uracil exhibited the protective effects on CCl4-induced hepatic injury, a pattern identical to or very similar to that observed with crude extracts of Trionyx carapax. Thus it is concluded that uracil is the active component responsible for protection from CCl4-induced hepatic injury.

A single step extraction procedure for recovery of the anthelmintic drug levamisole (LEV) from aqueous solutions and calf serum was evaluated. Levamisole was extracted from aqueous solutions and calf serum with 1.5 ml of ethyl acetate. After evaporation to dryness, the LEV content of extracts was estimated by measuring LEV inhibition of bovine milk fat globule membrane alkaline phosphatase. Lipid interference with absorbance readings was eliminated by the addition of 1.0 ml of chloroform to the assay mixtures. The recovery of LEV from both aqueous samples and serum samples by this single step extraction procedure coupled with enzymatic assay was 90%. The effective range for serum LEV determination was 0.3 to 20 micrograms/ml.

Mechanisms for the abnormal copper (Cu) accumulation in the liver of LEC rats were examined using primary cultured liver parenchymal cells prepared from mutant LEC rats and those from control LEA rats (original strain). The Cu and metallothionein (MT) mRNA levels in the liver of LEC rats were caused to decrease to the same levels as those of LEA rats by removing Cu in vivo selectively with tetrathiomolybdate. Cu was taken up by LEC rat cells to the same extent as LEA rat cells by exposure to low medium Cu and to a higher extent by exposure to high medium Cu, while the MT mRNA level in LEC rat cells increased dose-dependently at a much higher rate than that in LEA rats. MT mRNA levels in both cells were comparable by exposure to cadmium, zinc and dexamethasone. The results indicate that expression of MT mRNA is selectively enhanced by Cu in LEC cells despite the fact that uptake of Cu is comparable with normal cells.

Hyperglycemia-induced cataractogenesis has been studied in rat lenses cultured in 50 mM glucose using an inverted microscope connected with a Universal C-mount and a CCD camera. Digital images were acquired and the opacity was determined by quantitating the transmitted light. Antioxidants, butylated hydroxy toluene (BHT) and 6-hydroxy-2,5,7,8-tetramethenyl-chroman-2-carboxylic acid (Trolox) provided good protection against 50 mM glucose-induced cataractogenesis in rat lenses for upto 8 days. Sorbitol levels in the 50 mM glucose+antioxidant groups were approximately 1.5 mM fold higher than in 50 mM glucose. The results, besides further demonstrating that oxidative damage is the major mechanism of sugar-induced cataractogenesis, show that Trolox or related amphipathic compounds could be of therapeutic use in the prevention of diabetic cataracts.

To examine whether serum collagenase activity reflects the amount of collagenase activity in the fibrotic liver of rats, we simultaneously measured serum and hepatic collagenase activities in rats with carbon tetrachloride-induced liver injury. Serum collagenase was measured after reactivation by denaturing and dissociating the inhibitors with potassium thiocyanate and aminophenylmercuric acetate, while hepatic collagenase was measured after the removal of plasma protein and activation with aminophenylmercuric acetate. Serum and hepatic collagenase activities increased in the carbon tetrachloride-treated rats with the progression of liver fibrosis, and both activities of collagenase were closely correlated each other. These results suggest that serum collagenase activity measured in these assay conditions could be used as a noninvasive marker for hepatic collagenolysis in carbon tetrachloride-treated rats.

In rats intoxicated with doxorubicin, vasomotor responses were evaluated 12 hr after the last dosage. In rats pretreated with doxorubicin, hypertensive responses to L-norepinephrine and L-epinephrine, and hypertension by occlusion of both common carotid arteries were significantly (p < 0.05) reduced when compared with controls. Doxorubicin pretreatment also significantly reduced the arterial hypotension due to L-isoprenaline. In rats intoxicated with doxorubicin, pretreatment with L-sulpiride (12.5 to 50 mg/Kg/day for 30 days in drinking water ad libitum) did not modify the effects of doxorubicin on vasomotor reactivity. In contrast, pretreatment with amitriptyline (12.5 to 50 mg/Kg/day in drinking water ad libitum for 30 days) potentiated the inhibitory effects of doxorubicin on vasomotor responses. In conclusion, our research shows that doxorubicin intoxication induces a significant reduction of alpha- and beta-adrenergic reactivity and of baroreceptor activity.