Biomedical subjects

J Sudo

Publications and source records attributed to J Sudo.

58 records · Page 4Linked to original sources

PubMed1982

Cyclic AMP-dependent protein kinase activity and endogenous protein phosphorylation in isolated cortical segments of rabbit nephron.

Cyclic AMP-dependent protein kinase activity and endogenous protein phosphorylating activity are reported for 6 cortical segments of the rabbit nephron which were microdissected and collected according to their morphology. The 6 cortical nephron segments, namely the glomerulus (Glm), proximal convoluted tubule (PCT), proximal straight tubule (PST), cortical ascending limb of Henle's loop (CAL), distal convoluted tubule (DCT), and cortical collecting tubule (CCT), showed protein kinase activities which were increased 1.8-4.9 fold by 10(-6) M cyclic AMP in the presence of histone IIA, histone f2b or histone f3 as a protein substrate. However, all these segments showed little or no cyclic AMP dependent increase of activity with either protamine or alpha-casein as a protein substrate. Cyclic AMP increased the endogenous protein phosphorylation of Glm (10(-6) M cyclic AMP), of CAL (10(-7) and 10(-8) M cyclic AMP), of DCT (10(-6) M cyclic AMP) and of CCT (10(-8), 10(-7) and 10(-6) M cyclic AMP). In contrast, PCT showed decreased endogenous protein phosphorylation in the presence of 10(-7), 10(-5) and 10(-4) M cyclic AMP.

Animals↗

PubMed1981

[Distributions of peptidases in the metabolization of peptide hormones, particularly angiotensin II, along the isolated single nephron of rat (author's transl)].

The present study was undertaken to investigate the peptidases which degrade peptide hormones, particularly angiotensin II (AII), in the isolated rat nephron segments. These peptidases include leucine aminopeptidase, aminopeptidase A, cystine aminopeptidase, "trypsin-like enzyme(s)", "chymotrypsin-like enzyme(s)", postproline cleaving enzyme, and converting enzyme. The metabolic ability of [3H]-AII in each nephron segment, was also studied. The activities of these peptidases were exclusively higher in proximal tubules than in other segments. In the proximal tubule, only "trypsin-like enzyme(s)" showed the highest activity in pars convoluta, however, the other peptidases showed the highest activities in pars recta. The activities of aminopeptidase A, "trypsin-like enzyme(s)", and post-proline cleaving enzyme, were also high in the glomerulus. The activities of these peptidases were hardly detectable in distal nephron segments. From the investigation of the metabolic ability of [3H]-AII in each nephron segment, AII was found to be highly metabolized both in the glomerulus and in the proximal tubule, especially in the pars recta. AII was converted to angiotensin III (AIII) mainly in the glomerulus. All these findings suggest that peptide hormones including AII filtrated through the glomerulus are metabolized in the proximal tubule and that the conversion from AII to AIII occurs mainly in the glomerulus.

Aminopeptidases↗

PubMed1980

[Evaluation of nephrotoxic site in rat proximal tubule: intrarenal distributions of three enzymes and effects of mercuric chloride and gentamicin on their excretion into urine (author's transl)].

Intrarenal distributions of three enzymes, gamma-glutamyl transpeptidase (gamma-GTP), alkaline phosphatase (Al-p) and leucine aminopeptidase (LAP) were determined using six segments of nephrons. These enzymes were localized only in the proximal tubule. Intra-proximal distributions of the enzymes, however, were not uniform. The order of each enzyme activity in three segments of the proximal tubule, S1, S2 and S3 was as follows: Formula: (See Text) With subcutaneous administration of HgCl2 (1.0 mg/kg/day), urinary excretions of all three enzymes were increased from the 1st to the 2nd day and then decreased to the control level. However, after intraperitoneal administration of gentamicin sulfate (40 mg/kg/day), only Al-p activity in urine was significantly increased on the 1st day. Because of the lack of increasing blood levels of these enzymes after treatment, increased urinary excretions of the enzymes probably originate from the kidney, particularly the proximal tubule. The prominently increased excretion of gamma-GTP and LAP after HgCl2 treatment means that HgCl2 might damage S2 and S3, because the excretory patterns of the three enzymes were similar to their distribution profiles in S2 and S3. On the other hand, the toxic action of GM may be localized in S1 portion, in which Al-p activity proved to be highest among the three enzymes.

Alkaline Phosphatase↗

PubMed1979

Glucose dehydrogenase (hexose 6-phosphate dehydrogenase) and the microsomal electron transport system. Evidence supporting their possible functional relationship.

The ability of a microsomal enzyme, glucose dehydrogenase (hexose 6-phosphate dehydrogenease) to supply NADPH to the microsomal electron transport system, was investigated. Microsomes could perform oxidative demethylation of aminopyrine using microsomal glucose dehydrogenase in situ as an NADPH generator. This demethylation reaction had apparent Km values of 2.61 X 10(-5) M for NADP+, 4.93 X 10(-5) m for glucose 6-phosphate, and 2.14 X 10(-4) m for 2-deoxyglucose 6-phosphate, a synthetic substrate for glucose dehydrogenase. Phenobarbital treatment enhanced this demethylation activity more markedly than glucose dehydrogenase activity itself. Latent activity of glucose dehydrogenase in intact microsomes could be detected by using inhibitors of microsomal electron transport, i.e. carbon monoxide and p-chloromercuribenzoate (PCMB), and under anaerobic conditions. These observations indicate that in microsomes the NADPH generated by glucose dehydrogenase is immediately oxidized by NADPH-cytochrome c reductase, and that glucose dehydrogenase may be functioning to supply NADPH.

Aminopyrine N-Demethylase↗