The application of biochemical methods involving enzyme assays in the study of certain pathological conditions, studies with isocitrate dehydrogenase and b-glucuronidase

The thesis consists of two separate studies on two enzymes which have potentially useful applications in the biochemical study of various human diseases. In Part 1, the activity of the enzyme, is citrate dehydrogenase, in serum of patients with diseases involving the liver or biliary tract, was studied and compared with established biochemical tests of liver function, in order to assess its application to the differential diagnosis of jaundice. Particular attention was paid to results on patients with obstructive jaundice as previous authors have reached differing conclusions of the ultimate usefulness of this enzyme, due to the equivocal results shown in these cases. Very high values were found in severe, acute breakdown of liver cells. Those coincided with large increases in activity of two other enzymes used in the diagnosis of acute hepatic damage - serum giutamic-oxalacetic transaminase and serum glutamic-pyruvic transaminase. The serum isocitrate dehydrogenase was extremely sensitive in detecting liver cell damage, even at a subclinical level, and was comparable and perhaps slightly superior to the serum transaminases in this respect, while all three enzymes were very much more sensitive than other conventional tests of liver function. In chronic liver damage, variable values for serum isocitrate dehydrogenase were found, with only small to moderate increases which could not be related to the clinical state of the patient. Higher values were found in biliary cirrhosis than in portal cirrhosis. The enzyme results were significantly correlated with the transaminase results, but not with the other liver function tests. In obstructive jaundice, the enzyme was elevated in the serum of over 50% of the cases, and particularly high values were associated with secondary involvement of the liver in malignant oases, and acute inflammation of the biliary tract in benign obstructive jaundice. The enzyme could not be used to differentiate malignant from non-malignant cases, and was not related to the severity or duration of the biliary retention. In these cases, the enzyme was not closely related to serum transaminase values. It was concluded that the enzyme did not offer great advantages in the differential diagnosis of jaundice due to the abnormal values which may be found in obstructive jaundice. However, it was an easily estimated enzyme, very sensitive for detecting and assessing acute damage to liver cells, and could be a useful adjunct or alternative to the serum transaminasess Part R involved the study of the enzyme, p-glucuronidase, in various biological material taken from patients with carcinoma of the cervix uteri. Biopsy specimens of cervical carcinoma wore obtained and fractionated by homogenisation and differential centrifugation into three cytoplasmic fractions - mitochondria, miorosomes and soluble supernatant. p-Glucuronidase activity was measured in each fraction and the results compared with specimens eV non-malignant corvix treated in the ammo way. The activity of the carcinoma specimens was found to be considerably higsher than non-malignant specimens in the majority or caeca. Xneroasee in p-glucurenldase activity were mainly in the soluble supernatant fraction and not in particle enzyme even though tho enoyme had previously boon doocribod no located mainly within cytoplasmic particles. There was no correlation with the enzyme activity and dearie of malignancy of the cervical lesion. Sample of cervical carcinoma were taken before and aft treatment oi the lesion by irradiation from radium implant at and their 0.glucuronidase activity compared. There was not a uniform change in enzyme activity following radiation duo to larao unexplained increases and decreases being observed. The excretion of p-gluecuronidase in urine of patient with cervical carcinoma receiving radiotherapy was followed over the Pu11 course of treatment. Pronounced increase in excretion of the enzyme following radium treatment wove obaorvod in the majority of patients studied and the pattern of 0.61ucuronidaso excretion could be related to the enzyme activity of the tissue being irradiated. There was also increase in p-glucuronidase activity of the serum in these patients, and the results indicated that radiation of the lesion caused mobilisation or the enzyme into the patient circulation, which was then cleared by the kidneys into the urine