Pharmacokinetics of diaspirin cross-linked haemoglobin in a rat model of hepatic cirrhosis

Comparison of the Pharmacokinetic Properties of Hemoglobin-Based Oxygen Carriers

Hemoglobin (Hb) is an ideal material for use in the development of an oxygen carrier in view of its innate biological properties. However, the vascular retention of free Hb is too short to permit a full therapeutic effect because Hb is rapidly cleared from the kidney via glomerular filtration or from the liver via the haptogloblin-CD 163 pathway when free Hb is administered in the blood circulation. Attempts have been made to develop alternate acellular and cellular types of Hb based oxygen carriers (HBOCs), in which Hb is processed via various routes in order to regulate its pharmacokinetic properties. These HBOCs have been demonstrated to have superior pharmacokinetic properties including a longer half-life than the Hb molecule in preclinical and clinical trials. The present review summarizes and compares the pharmacokinetic properties of acellular and cellular type HBOCs that have been developed through different approaches, such as polymerization, PEGylation, cross-linking, and encapsulation.

Biochemical and histopathological study in rats intoxicated with carbontetrachloride and treated with camel milk

The unique characters of camel’s milk make it used extensively in the field of medicine as anti-microbial, anti-diabetic and hepatoprotective agent. The lack of studies demonstrating the protective effect of camel’s milk against hepatotoxic compound was the main reason beyond the conduction of the current experiment which aimed to investigate the protective effects of camel’s milk against carbontetrachloride (CCl₄) induced hepatotoxicity. Therefore, 24 rats were fed on standard diet and divided into four groups. Rats of the first group and second groups were injected i/p with paraffin oil and received either tap water (control 1) or camel’s milk (control 2), respectively. Rats of the third and fourth groups were injected i/p with CCl₄ and received either tap water or camel’s milk, respectively. At the end of the experiment (5 weeks), blood and liver samples were collected for biochemical and histopathological analysis. The present findings revealed that, CCl₄ elevated serum enzyme activities of liver and some biochemical parameters, but these effects were prevented by the treatment of rats with camel milk. Histopathologically, a great amount of mononuclear cells infiltration, necrotic cells and few fibroblasts were observed in liver of CCl₄ treated group. The present study concluded that camel milk treatment may play a protective role against CCl₄-induced liver damages in rats. These protective effects were in the form of improving of liver enzyme activities, blood biochemical parameters and histological picture of liver of intoxicated rats. In the future, examination of the liver protective effect of camel milk against CCl₄ in dose dependant manner could be investigated.

Microbial metabolism of biologically active secondary metabolites from Nerium oleander L

Ursolic acid (1) and kaempferol (3) are two major constituents of the Mediterranean plant Nerium oleander L. Microbial metabolism of (1) with Aspergillus flavus (ATCC 9170) resulted in the formation of 3-oxo-ursolic acid derivative, ursonic acid (2). On the other hand, Cunninghamella blakesleeana (ATCC 8688A) was able to convert (3) into kaempferol 3-O-beta-D-glucopyranoside (4) as well as the new natural product kaempferol 4'-sulfate (5). Incubation of kaempferol with Mucor ramannianus (ATCC 9628) led to the isolation of one metabolite identified as kaempferol 4'-O-alpha-L-rhamnopyranoside (6). Transformation of kaempferol to the new compound kaempferol 7-O-beta-D-4-O-methylglucopyranoside (7) and herbacetin 8-O-beta-D-glucopyranoside (8) was observed after fermentation with Beauveria bassiana (ATCC 13144). Cytotoxic as well as antioxidant activities of the isolated metabolites were determined.

Role of haptoglobin on the uptake of native and beta-chain [trimesoyl-(Lys82)beta-(Lys82)beta] cross-linked human hemoglobins in isolated perfused rat livers

The role of haptoglobin in liver cell entry of acellular native hemoglobin, and cross-linked human hemoglobin, a potentially useful oxygen-carrier alternative in transfusion medicine, was examined in the recirculating, perfused rat liver preparation. Doses of tritiated native human or beta-chain [trimesoyl-(Lys82)beta-(Lys82)beta] cross-linked human hemoglobin were preincubated with haptoglobin-containing rat plasma or Krebs Henseleit bicarbonate buffer for 30 min and used for perfusion. Concentrations (dpm/ml) in reservoir, before and after separation of the hemoglobins and metabolites by gel filtration fast protein liquid chromatography column chromatography, were similar, showing mostly the presence of intact hemoglobin. Each hemoglobin species underwent a rapid distribution phase, followed by a protracted elimination phase. The radioactivity in bile at 3 h consisted of low molecular weight metabolites, and cumulative excretion was slightly higher when rat plasma was present: for native hemoglobin, 7.1 +/- 1.6% versus 9.2 +/- 2.1% dose; for cross-linked hemoglobin, 5.0 +/- 1.7% versus 7.2 +/- 0.8% dose. Data fit to a two-compartment model and physiologically based model revealed a significantly faster influx clearance (CL(influx)) over the metabolic intrinsic clearance (CL(int, met)). The ratios of CL(influx)/CL(int, met) were 125 and 535 for native hemoglobin in the absence and presence of rat haptoglobin, respectively, according to compartmental analyses; the ratios were 25 and 53, respectively, according to physiological modeling. The corresponding ratios for cross-linked hemoglobin in the absence and presence of rat haptoglobin were 55 and 81, respectively, and 24 and 70 for compartmental and physiological modeling. Although haptoglobin enhanced the hepatic internalization of the hemoglobins, the impact on the net clearance was lessened since degradation was the rate-limiting step.

Redox biology of blood revisited: the role of red blood cells in maintaining circulatory reductive capacity

There is an increasing recognition of the role of red blood cells (RBCs) in cell signaling above and beyond its oxygen (O(2))-carrying function. A recent forum published in the December 2004 issue of Antioxidants & Redox Signaling focused on redox biology of blood and the intricate signaling pathways of RBCs or its free components, i.e., hemoglobin, with the vasculature. The forum provided an up-to-date source of information on this emerging and exciting area of blood biology and the underlying redox chemistry. In the current short review, we have revisited the topic of redox biology of blood and focused on yet another emerging area of research, which deals with the reductive power of blood and the physiological Redox Signal.

Reduction of carbon tetrachloride-induced nephropathy by melatonin administration

The aim of this study was to investigate possible protective effects of melatonin on carbon tetrachloride (CCl4)-induced renal damage in rats. A total of 24 animals were divided into three equal groups: the control rats received pure olive oil subcutaneously, rats in the second group were injected with CCl4 (0.5 ml kg-1, s.c. in olive oil) and rats in the third group were injected with CCl4 (0.5 ml kg-1) plus melatonin (25 mg kg-1, s.c. in 10% ethanol) every other day for 1 month. At the end of the experimental period, the animals were sacrificed and blood samples were collected. The kidneys were removed and weighed. Urea and creatinine levels were determined in blood samples. Histopathological examination of the kidney was performed using light microscopic methods. Administration of CCl4 significantly increased relative kidney weight (g per 100 g body weight) and decreased serum urea levels compared to controls (p<0.01). Melatonin treatment significantly (p<0.01) reduced relative kidney weight, and it produced a statistically equal (p=0.268) relative weight with the kidneys of control rats. CCl4 administration alone also caused histopathologically prominent damage in the kidney compared to the control group. Glomerular and tubular degeneration, interstitial mononuclear cell infiltration and fibrosis, vascular congestion around the tubules, and interstitial haemorrhage in perivascular areas were observed in the renal cortex and cortico-medullary border. However, the affect of CCl4 on the medulla was limited. Melatonin provided protection against CCl4-induced renal toxicity as was evident by histopathological evaluation. In view of the present findings, it is suggested that melatonin protects kidneys against CCl4 toxicity.

The Pharmacokinetics of Hemoglobin-Based Oxygen Carrier Hemoglobin Glutamer-200 Bovine in the Horse

Hemoglobin-glutamer-200 (HBOC-200) is a hemoglobin (Hb)-based oxygen carrier (HBOC) comprising glutaraldehyde-polymerized bovine Hb. In this study, we sought to determine the pharmacokinetics of this first generation HBOC after IV infusion of 32.5 g of HBOC-200 solution in horses. Quantification of HBOC-200 in equine plasma and urine was performed using a method recently developed by our laboratory. The elimination from plasma was based on size distribution of the bovine Hb polymer. The decline of plasma concentration-time curve of HBOC-200 was described by a noninterchanging 2-compartmental model. The median elimination half-lives of the small and large aggregates were 1.3 and 12.0 h, respectively. Of the HBOC-200 infused, 47.0% was eliminated as the smaller molecular weight and 53% as the larger molecular weight polymers. The area under the plasma concentration-time curve was 5143.1 microg.h(-1).mL(-1). The volumes of distribution of the small and large aggregates were 86.9 and 63.9 mL/kg and the clearances were 42.1 and 3.8 mL.kg(-1).h(-1), respectively. In conclusion, elimination of first generation HBOCs was shown to be more complex than previously assumed because of the heterogeneous nature of these solutions. Mammalian species dispose of Hb using similar mechanisms, and there is no unique metabolic process in the horse that would not allow a logical extension of the general interpretation of this study.

Caffeic acid phenethyl ester protects kidneys against carbon tetrachloride toxicity in rats

Caffeic acid phenethyl ester (CAPE), an active component of propolis produced by honeybees, exhibits antioxidant and anti-inflammatory properties. The aim of this study was to investigate possible protective effects of CAPE on carbon tetrachloride (CCl4)-induced renal damage in rats. A total of 24 animals were divided into three equal groups: the control rats received pure olive oil subcutaneously, rats in the second group were injected with CCl4 (0.5 ml/kg, s.c. in olive oil) and rats in the third group were injected with CCl4 (0.5 ml/kg) plus CAPE (10 micromol/kg, i.p.) every other day for one month. At the end of the experimental period, the animals were sacrificed and blood samples were collected. Serum urea and creatinine levels and renal malondialdehyde (MDA) contents were determined. Histopathological examination of the kidney was also performed using light microscopic methods. It was found that kidney MDA levels were increased significantly following CCl4 exposure and this increase was significantly inhibited by CAPE treatment, while no significant changes were observed in serum urea and creatinine levels. CCl4 administration alone also caused histopathologically prominent damage in the kidney compared to the control group. Glomerular and tubular degeneration, interstitial mononuclear cell infiltration and fibrosis, and vascular congestion in the peritubular blood vessels were observed in the renal cortex. With exception of rare vascular congestions, these histopathological changes were disappeared in rats treated with CCl4 plus CAPE. In view of the present findings, it is suggested that CAPE protects kidneys against CCl4 toxicity.

Effects of melatonin on carbon tetrachloride-induced changes in rat serum

Carbon tetrachloride (CCl4) is a volatile organic chemical, which causes tissue damage, especially to the liver and kidney. In experimental animals it has been shown to be carcinogenic. This study was designed to evaluate the effects of exogenous melatonin administration on the CCl4-induced changes of some biochemical parameters in rat blood. Twenty-four male Wistar rats were randomly divided into three equal groups: Control, CCl4 and CCl4 plus melatonin (CCl4+MEL). Rats in CCl4 group were injected subcutaneously with CCl4 0.5 ml/kg in olive oil while rats in CCl4+MEL group were injected with CCl4 (0.5 ml/kg) plus melatonin (25 mg/kg in 10% ethanol) every other day for one month. Control rats were treated with olive oil. Serum urea, creatinine, total protein, albumin, aspartate aminotransferase (AST), alanine aminotransferase (ALT), total and conjugated bilirubin, alkaline phosphatase (ALP), gamma-glutamyl transferase (gamma-GT), total iron, and magnesium levels were determined. Serum AST, ALT, total and conjugated bilirubin, ALP, gamma-GT, and total iron levels were significantly higher in CCl4-treated rats than in the controls, while urea, total protein, and albumin levels were significantly lower. Melatonin treatment did not cause a significantly change in serum urea, total protein, and albumin levels. However, the elevations in AST, ALT, total and conjugated bilirubin, ALP, gamma-GT, and total iron levels induced by CCl4 injections were significantly reduced by melatonin. On the other hand, melatonin administration significantly decreased serum magnesium levels. These results indicate that melatonin could be a protective agent against the CCl4 toxicity in rats, most likely through its antioxidant and free radical scavenger effects.

Blood substitutes

Blood substitutes are solutions intended to replace transfusion of banked red blood cells. Several variations of products based on either hemoglobin (animal or human) or perfluorocarbon emulsions are in advanced stages of clinical development. The need for such products is pressing as shortages of banked blood worsen and awareness of the dangers of blood transfusion increases. Animal and human studies with these cell-free oxygen carriers have led to new concepts of how oxygen is delivered to tissue and how the microcirculation is regulated. Although development of products is exciting and timely, understanding how they function to perfuse and oxygenate tissue could be at least as important. Because cell-free oxygen carriers will perfuse every organ of the body, their effects are far-reaching, and the transition from the laboratory to the bedside can be expected to be slow and deliberate. Comparison of oxygen carriers with more traditional starch-based products provides new insight into the interaction of oxygen transport, microvascular perfusion, and blood volume expansion.