Irwin M. Arias

Studies of Hepatic Excretory Function

17-alpha-ethinyl-17-beta-hydroxy-5-(10) -estren-3-one (norethynodrel) and ethinylestradiol 3-methyl ether (mestranol) were administered intermittently and continuously in doses recommended for suppression of ovulation to women with neither clincial nor chemical evidence of liver disease. 24 women who were from 23-33 years of age were involved in the study. Reversible reduction of the hepatic transport maximum for bromsulfalein was observed; relative hepatic storage was unimpaired; and the dye was retained in plasma primarily as a conjugate. The administration of estradiol (2.5 mg per day for 10 days) did not alter the transport maximum the storage or the percentage of conjugated dye in plasma. The results suggest that the effect of norethynodrel and mestranol on bromsulfalein metabolism is probably related to the progestin that regularly interferes with the transfer of bromsulfalein conjugates from the liver cell into the bile. Light and electron microscopical and histochemical examinations of 2 liver biopsies were within normal limits. It is recommended that caution be exercised in the clinical use of these and related drugs in children or adults with hereditary developmental or acquired defects in hepatic excretory function.

Isolation of multiple normal and functionally defective forms of uridine diphosphate-glucuronosyltransferase from inbred Gunn rats.

Gunn rats are a mutant strain of Wistar rats that have unconjugated hyperbilirubinemia due to absence of hepatic uridine diphosphate-glucuronosyltransferase (UDPGT; EC. 2.4.1.17) activity toward bilirubin. We isolated five UDPGT isoforms from solubilized microsomal fractions from liver of inbred Wistar (RHA) rats and congeneic Gunn rats. UDPGT isoform V (elution pH 7.5) from Wistar (RHA) rats is active toward bilirubin and 4-hydroxydimethylaminoazobenzene. The corresponding isoform from Gunn rat liver was enzymically inactive but exhibited normal elution pH and mobility on NaDodSO4/polyacrylamide gel electrophoresis (Mr 53,000), and was recognized by a UDPGT-specific antiserum. UDPGT isoform I (elution pH 8.7) from Wistar (RHA) and Gunn rats was active toward 4-nitrophenol. The isoform from Gunn rat liver had only 10% of normal UDPGT activity, however UDPGT activity increased to normal upon addition of 15 mM diethylnitrosamine in vitro. Isoforms II (elution pH 8.4), III (elution pH 8.0), and IV (elution pH 7.8) from Gunn rats had normal UDPGT activities, except that Isoform IV was inactive toward bilirubin.

Abnormal Sulfobromophthalein Metabolism in Rotor's Syndrome and Obligate Heterozygotes

Rotors syndrome is an inheritable disorder characterized by chronic nonhemolytic, predominantly conjugated hyperbilirubinemia without abnormal hepatic pigmentation.1 2 3 4 Because of clinical simi...

Gamma Glutamyl Transpeptidase : Measurement and Development in Guinea Pig Small Intestine

Extract: A modification of a previous method for the assay of γ glutamyl transpeptidase (GGTP) was developed. Substrate solubility difficulties alluded to by other investigators were avoided by employing heating and solubilization of the chromogenic substrate γ glutamyl-β-naphthylamide in a medium of carbonate 0.05 M and Tris buffer 0.1 M at pH 9.5. The kinetics and conditions for such an assay are described. Whole intestinal homogenates of adult male guinea pigs were used as the source of the enzyme.The developmental pattern of this enzyme was determined in fetuses at 55 and 63 days of gestation and at varying times from 1 to 90 days of age. A total of 69 animals was assayed. The general pattern was that of high specific activity during prenatal life, with a rapid decline during the neonatal period (3–24 days of age) and a slight increase after 55 days of age.Other guinea pig organs were studied. Liver and kidney were found to contain enzyme activity greater than that of the intestine. Subcellular fractionation of intestinal mucosa using ultracentrifugation revealed a twenty-fold enrichment of activity in jejunal brush border membrane, compared with whole jejunal homogenates when expressed as specific enzyme activity per mg of protein. The stability characteristics of GGTP disclosed no loss of specific activity when stored at −28° for 50 days.This simple enzyme assay, stability of the enzyme when frozen, subcellular distribution in the intestinal brush border membrane, and an unusual developmental pattern made this enzyme a useful adjunct to the study of intestinal protein metabolism.Speculation: The unique ability of GGTP to hydrolyze γ glutamic acid-peptide bonds and the location of the enzyme in the intestinal brush border suggest a role for this enzyme in the metabolism of an unusual group of physiologically important peptides such as glutathione, folic acid, and gluten-gliadin. The significance of these γ-bonded compounds may now be approached in order to investigate the role of this enzyme in gluten enteropathy and related disorders.

Hepatic conversion of bilirubin monoglucuronide to diglucuronide in uridine diphosphate-glucuronyl transferase-deficient man and rat by bilirubin glucuronoside glucuronosyltransferase.

The microsomal enzyme uridine diphosphate (UDP) glucuronate glucuronyltransferase (E.C. 2.4.1.17) catalyzes formation of bilirubin mono-glucuronide from bilirubin and UDPglucuronic acid. Bilirubin glucuronoside glucuronosyltransferase (E.C. 2.4.1.95), an enzyme concentrated in plasma membrane-enriched fractions of rat liver, converts bilirubin monoglucuronide to bilirubin diglucuronide. Bilirubin glucuronoside glucuronosyltransferase activity was studied in homogenates of liver biopsy specimens obtained from patients with the Crigler-Najjar syndrome (Type I) and in subcellular liver fractions of rats homozygous for UDP glucuronate glucuronyltransferase deficiency (Gunn strain). In patients with the Crigler-Najjar syndrome (Type I) and in Gunn rats, hepatic UDPglucuronate glucuronyltransferase activity was not measurable; however, bilirubin glucuronoside glucuronosyltransferase activity was similar to that in normal controls. The subcellular distribution of bilirubin glucuronoside glucuronosyltransferase activity in Gunn rat liver was similar to the distribution observed in normal Wistar rat liver.When bilirubin monoglucuronide was infused intravenously into Gunn rats, 29+/-5% of the conjugated bilirubin excreted in bile was bilirubin diglucuronide. After transplantation of normal Wistar rat kidney, which contained UDPglucuronate glucuronyltransferase activity, in Gunn rats, the serum bilirubin concentration decreased by 80% in 4 days. The major route of bilirubin removal was biliary excretion of conjugated bilirubin, approximately 70% of which was bilirubin diglucuronide. Although patients with the Crigler-Najjar syndrome (Type I) and Gunn rats lack UDP glucuronate glucuronyltransferase, their livers enzymatically convert bilirubin monoglucuronide to diglucuronide in vitro. Conversion in bilirubin monoglucuronide to diglucuronide was demonstrated in Gunn rats in vivo.

Absorption of Radioactive Vitamin B12 in Nonanemic Patients with Combined-System Disease

BEFORE the advent of liver or vitamin B12 treatment of pernicious anemia, approximately 80 per cent of patients who died of this disease had neurologic signs resulting from demyelinization of the posterior and lateral columns of the spinal cord.1 This neurologic disorder has been variously termed combined-system disease, posterolateral sclerosis, subacute combined degeneration of the spinal cord and funicular degeneration. Its pathology, clinical course and response to treatment are well kno-n.2 3 4 5 6 7 In vitamin B12 deficiency, anemia usually precedes the development of neurologic signs and symptoms, but occasionally this sequence is reversed and extensive neurologic damage may occur in .xa0.xa0.

Coproporphyrin excretion in amniotic fluid and urine from premature infants: a possible maturation defect.

Extract: Coproporphyrin analysis was performed on urine from 17 male and 7 female premature infants (birth wt 1.5–4.5 kg, average 1.7 kg). Six specimens of amniotic fluid obtained before elective abortion induced by saline solution infusion were also examined. Normal adult control subjects excreted 24.6% ± 5.6% of total coproporphyrin as coproporphyrin I. Twenty-three premature infants excreted 59.4% ± 17.3% as coproporphyrin I, significantly higher amounts than control subjects (P < 0.001). Coproporphyrin I excretion in six specimens of amniotic fluid was 84.9% ± 10.4%, significantly higher than in urine from adults and premature infants (P < 0.001).Speculation: These results raise the possibility of a similar hepatic excretory defect in porphyrin metabolism in the developing fetus and in the Dubin-Johnson syndrome. In the former, the defect is developmental; in the latter, it is lifelong and is present in obligate heterozygotes. Uroporphyrinogen III cosynthetase normally catalyzes conversion of porphobilinogen to isomer III rather than isomer I porphyrins. Developmental deficiency of this enzyme may be responsible for the observed pattern of coproporphyrin isomers seen in the fetus and neonate.