Alcohol dehydrogenase in human tissues: localisation of transcripts coding for five classes of the enzyme

Tissue distribution of the five identified classes of human alcohol dehydrogenase was studied by assessment of mRNA levels in 23 adult and four fetal tissues. Alcohol dehydrogenase of class I was found in most tissues, brain and placenta excluded, but expression levels among tissues differed widely. The distribution pattern of class III transcripts was consistent with those of housekeeping enzymes while, in contrast, class IV transcripts were found only in stomach. Transcripts of multiple length were detected for most classes and were due to different gene products arising through the use of different poly-A signals or transcription from different gene loci. Both class II and class V showed a pattern of liver-enriched expression. However, low mRNA levels were detected also in stomach, pancreas and small intestine for class II, and in fetal kidney and small intestine for class V. Significantly higher levels of class V transcripts were present in fetal liver when compared with levels in adult liver, which suggests that human class V is a predominantly fetal alcohol dehydrogenase.

Aldehyde dismutase activity of human liver alcohol dehydrogenase

Human alcohol dehydrogenases of class I and class II but not class III catalyse NAD+-dependent aldehyde oxidation in addition to the NADH-dependent aldehyde reduction. The two reactions are coupled, i.e. the enzymes display dismutase activity. Dismutase activity of recombinantly expressed human class I isozymes beta1beta1 and gamma2gamma2, class II and class III alcohol dehydrogenases was assayed with butanal as substrate by gas chromatographic-mass spectrometric quantitations of butanol and butyric acid. The class I gamma2gamma2 isozyme showed a pronounced dismutase activity with a high kcat, 1300 min(-1), and a moderate Km, 1.2 mM. The class I beta1beta1 isozyme and the class II alcohol dehydrogenase showed moderate catalytic efficiencies for dismutase activity with lower kcat values, 60-75 min(-1). 4-Methylpyrazole, a potent class I ADH inhibitor, inhibited the class I dismutation completely, but cyanamide, an inhibitor of mitochondrial aldehyde dehydrogenase, did not affect the dismutation. The dismutase reaction might be important for metabolism of aldehydes during inhibition or lack of mitochondrial aldehyde dehydrogenase activity.

Progression of canine mammary tumours as reflected by DNA ploidy in primary tumours and their metastases

Thirty dogs with metastasizing mammary tumours (carcinomas, n = 22; sarcomas, n = 8) were necropsied. Flow cytometric DNA analysis was carried out on frozen primary tumours and on selected metastases from the dogs. Ductular carcinomas (n = 13) had a varying growth pattern, in terms of histology, in both the primary tumours and metastases and between different metastases. The different types of DNA ploidy, including hypodiploidy, in the primary ductular carcinomas were also seen in the tumour metastases. Dogs with primary anaplastic carcinomas (n = 7) had multiple metastases, which were in most cases near-diploid or hyperdiploid. Two dogs had spindle-cell carcinomas, which were hypodiploid in both the primary tumour and the metastases. The DNA ploidy in the metastases was retained in 16 of the 22 dogs with primary carcinomas. Fibrosarcomas (n = 5) showed different types of DNA ploidy. In two of the three dogs with diploid or near-diploid osteosarcomas, the DNA ploidy was retained in the metastases. There was a statistically significant association between mammary tumours and metastases (P = 0.0001) in terms of both histological diagnosis and DNA ploidy. The association was retained when the carcinomas were tested separately (P = 0.0001); in the sarcomas it was retained weakly in terms of histology (P = 0.0183) but not DNA ploidy (P = 0.6659). The retention of the DNA ploidy in most carcinoma metastases indicated that selection of DNA ploidy had taken place prior to metastasis. The differences in patterns of DNA ploidy between ductular and anaplastic carcinomas may reflect different pathogenesis in these types of canine mammary tumour.

Coacute heparin: a new simple monotest for monitoring heparin treatment

Anti-Factor Xa methods have been generally accepted for the monitoring of heparin treatment, mainly due to their sensitivity to LMW heparin and excellent performance on automated equipment. When such equipment is not available, as in small laboratories or on the night shift, there is a need for a simple manual method. In the present method activated Factor X and a chromogenic peptide substrate are colyophilized in plastic cuvettes under conditions that avoid reaction between the two constituents. The assay is performed accordingly: Plasma (200 microL) is diluted in 3.0 mL predispensed Tris buffer containing dextran sulfate 8000 to avoid losses of heparin due to, for example, platelet factor 4. The diluted plasma (400 microL) is added to a cuvette. The reagents are rapidly dissolved and the reactions start. The rate of Factor Xa inhibition is proportional to the heparin activity. During the incubation, the substrate is also hydrolyzed by the remaining enzyme. This combination of reactions is insensitive to changes in temperature, making it possible to perform the assay at room temperature. After 10 minutes incubation, the reaction is stopped by adding 400 microL of 5% acetic acid. The absorbance is read in a well-calibrated photometer and the results plotted on a graph available in the kit. Eleven commercially available heparins have been tested with the assay and they all fell within a narrow range, showing the relevance of using a standard plot for all heparins. The LMW heparins behaved differently and it may also be that they demand different therapeutic strategies.