Biomedical subjects

N Shiota

Publications and source records attributed to N Shiota.

43 records · Page 3Linked to original sources

PubMed1994

Localization and quantitation of active renin in monkey kidney by radioinhibitor binding and in vitro autoradiography.

We developed an in vitro autoradiographic method to localize and quantify active renin in primate tissues. Active renin in monkey kidney sections was labeled with the primate specific renin inhibitor, 3H-CGP29287, and quantitated with autoradiography and computerized densitometry. Microscopic emulsion autoradiography was carried out to clarify the detailed localization of the binding. Non-specific binding to aspartyl proteases other than renin was blocked using 1 mumol/L of N-acetyl-pepstatin. To assess the usefulness of this procedure, binding of 3H-CGP29287 was examined both by film and emulsion autoradiography in the kidneys of monkeys (Macaca fuscata) that were given chronically either an angiotensin converting enzyme inhibitor (trandolapril), an angiotensin II receptor antagonist (E4177), or vehicle. 3H-CGP29287 was found to bind very selectively to the juxtaglomerular apparatus (JGA) under control conditions. In monkeys treated with trandolapril or E4177, 3H-CGP29287 binding was increased in proportion to the increase in renal renin concentration determined enzymatically; in these kidneys, emulsion autoradiography revealed radioinhibitor binding extending far from the JGA. The potency of a series of unlabeled renin inhibitor in competing for 3H-CGP29287 binding in the autoradiographic system closely paralleled their potencies, as determined in inhibiting renin by an enzymatic assay. This technique permits specific labeling of the catalytic site of renin in the monkey kidney sections.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed1994

Herbicide-resistant tobacco plants expressing the fused enzyme between rat cytochrome P4501A1 (CYP1A1) and yeast NADPH-cytochrome P450 oxidoreductase.

Transgenic tobacco (Nicotiana tabacum cv Xanthi) plants expressing a genetically engineered fused enzyme between rat cytochrome P4501A1 (CYP1A1) and yeast NADPH-cytochrome P450 oxidoreductase were produced. The expression plasmid pGFC2 for the fused enzyme was constructed by insertion of the corresponding cDNA into the expression vector pNG01 under the control of the cauliflower mosaic virus 35S promoter and nopaline synthase gene terminator. The fused enzyme cDNA was integrated into tobacco genomes by Agrobacterium infection techniques. In transgenic tobacco plants, the fused enzyme protein was localized primarily in the microsomal fraction. The microsomal monooxygenase activities were approximately 10 times higher toward both 7-ethoxycoumarin and benzo[a]pyrene than in the control plant. The transgenic plants also showed resistance to the herbicide chlortoluron.

Animals↗

PubMed1993

Activation of two angiotensin-generating systems in the balloon-injured artery.

Participation of angiotensin II in the myointimal proliferation following a vascular injury was postulated. This study assessed the potential involvement of the local angiotensin II-forming enzymes in injured arteries of dogs. The potential angiotensin II-forming enzymes are angiotensin-converting enzyme (ACE) and chymostatin-sensitive angiotensin II-generating enzyme (CAGE) which is highly homologous to or could be identical to the mast cell chymase. Both ACE and CAGE catalyze the conversion of angiotensin I to angiotensin II. We found that the enzymatic activities of ACE and CAGE, and the mRNA levels of ACE and chymase were increased in the injury-induced hypertrophied vessels. The results suggest that ACE and CAGE participate in the hypertrophy through the production of angiotensin II which is a growth promoter for vascular smooth muscle cells.

Angiotensin II↗

PubMed1993

Marked species-difference in the vascular angiotensin II-forming pathways: humans versus rodents.

Using isolated arteries, we demonstrated a marked difference in the angiotensin II-forming systems between human and rodent vessels. In human arteries, only 30-40% of the conversion of angiotensin I to angiotensin II depended on the angiotensin-converting enzyme (ACE), and the rest of the angiotensin II formation was ascribed to chymostatin-sensitive angiotensin II-generating enzyme (CAGE). On the contrary, angiotensin II formation in rodent arteries totally depended upon ACE, without any sign of CAGE involvement. Such a marked species-difference can be relevant to the reported difference between humans and rodents in the ACE inhibitor effects on the myointimal hyperplasia after intimal balloon injury.

Adult↗

PubMed1992

Nephrectomy and a newly identified binding site for angiotensin II in the rat adrenal cortex.

Angiotensin II (Ang II) binding sites in adrenal glands of nephrectomized rats were investigated by in vitro autoradiography using 125I-[Sar1,Ile8]Ang II as ligands. Ang II binding site was increased to 161% in the cortex and decreased to 67% in the medulla 48 h after nephrectomy. In the medulla, the AT2 antagonist (PD123177, 5 microM) inhibited specific binding by 90% whereas the AT1 antagonist (DuP753, 5 microM) inhibited by only 10%. In contrast, in the cortex, neither DuP753 (5 microM) nor PD123177 (5 microM) substantially inhibited the binding. Binding in the presence of either the AT1 or AT2 antagonist was abolished by the simultaneous presence of both antagonists. These results suggest the presence of a new Ang II binding site with unique pharmacological properties and differing from currently known subtypes of Ang II receptors, in the adrenal cortex after nephrectomy.

Adrenal Cortex↗

PubMed1992

Increase of angiotensin converting enzyme gene expression in the hypertensive aorta.

To investigate the possible role of vascular angiotensin converting enzyme (ACE) in the development and maintenance of hypertension, we examined aortic ACE messenger RNA (mRNA) levels in two-kidney, one clip (2K1C) hypertensive rats. The blood pressure was increased remarkably at 4 weeks (early stage) after clipping and remained elevated at 12 weeks (chronic stage). The aorta ACE mRNA levels were significantly elevated in both early and chronic stages concurrently with the increases in aortic ACE activity and blood pressure. The plasma renin activity rose markedly at 4 weeks, but returned to the normal level at 12 weeks. Neither ACE activity in the lung and plasma, nor ACE mRNA level in the lung was altered at either stage. The aorta and liver angiotensinogen mRNA levels and renal renin mRNA level were increased at 4 weeks but decreased at 12 weeks. These results indicate that the acceleration of all components in the renin-angiotensin system may contribute to the development of 2K1C hypertension in the early stage. In the chronic stage, the increased vascular ACE induced by the elevated ACE mRNA levels in the aorta may play the primary role in the acceleration of local angiotensin II formation and thus may sustain the hypertension.

Angiotensinogen↗

PubMedDate not supplied

Angiotensin II-generating system in dog and monkey ocular tissues.

1. Angiotensin II (AngII) is generated locally in several tissues, including ocular tissues. Recently, it has been suggested that in addition to angiotensin-converting enzyme (ACE), an alternative AngII-generating enzyme, chymase, is present in the present in the cardiovascular tissues of humans, monkeys and dogs and may be involved in the local production of AngII. The purpose of the present study was to determine whether chymase contributes to AngII generation in dog and monkey ocular tissues and to clarify the intraocular AngII-generating system. 2. Chymase-like and ACE activities were measured in dog and monkey ocular tissues, carotid artery, heart and lung. Their mRNA levels were quantified using the competitive reverse transcriptase-polymerase chain reaction (RT-PCR) method. 3. Chymase-like activity was detected in the anterior uveal tract, choroid and sclera in dog eyes, but not in the cornea, lens or fluid phase (vitreous body and aqueous humor). In monkey eyes, chymase-like activity was detected in the anterior uveal tract and it was higher here than in the heart. Angiotensin-converting enzyme activity was detected in the anterior uveal tract, choroid, retina, sclera and fluid phase in both dog and monkey eyes. Chymase and ACE mRNA were detected in tissues showing enzymatic activity. 4. These findings show for the first time that chymase, in addition to ACE, is expressed locally in dog and monkey ocular tissues and may be involved in local AngII generation in the eye.

Angiotensin II↗