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C Koseki

Publications and source records attributed to C Koseki.

29 records · Page 2Linked to original sources
PubMed1986

Difference in molecular size of receptors for alpha-rat atrial natriuretic polypeptide among the kidney, aorta, and adrenal gland as identified by direct UV-photoaffinity labeling.

In order to identify the molecular size of receptors for alpha-rat atrial natriuretic polypeptide (alpha-rANP), we utilized the direct UV irradiation method for photoaffinity labeling with the biologically active [125I] alpha-rANP. In the preparation of isolated glomerulus and the inner medullary collecting duct (IMCT)-rich fraction, the autoradiograms of the electrophoresed sodium dodecyl sulfate (SDS)-polyacrylamide gels showed a single radioactive band which is displaceable with unlabeled alpha-rANP. The dose-dependent displacement fit very well with a binding-inhibition curve representing the binding affinity of 6.5 X 10(-10) M. The molecular size of the ligand-receptor complex was about 65,000 daltons for both glomerulus and IMCT-rich fraction. In contrast, in homogenate of the aorta and adrenal gland, the ligand-receptor complex was 140,000 daltons.

Adrenal Glands↗
PubMed1986

Localization of binding sites for alpha-rat atrial natriuretic polypeptide in rat kidney.

To determine the intrarenal localization of receptors for atrial natriuretic polypeptide (ANP) in the rat, we performed autoradiography and binding assay by using 125I-labeled alpha-rat ANP (alpha-rANP). Autoradiography at the slice and microscopic level in the kidney and binding assay in isolated glomeruli demonstrated that receptors in the renal cortex were distributed mainly in glomeruli. Although dense silver grains were distributed diffusely both in inner medulla and outer stripe of outer medulla, a marked displacement of the grains was observed only in the inner medulla. Autoradiography at the microscopic level also showed that silver grains were distributed in the renal artery, renal pelvis, and inner medullary collecting tubule (IMCT) prepared by the microdissection method, but not in the arcuate artery, interlobular artery, and afferent or efferent arterioles. Specific binding was demonstrated in the isolated glomeruli and the preparation was rich in fragments of IMCT. Apparent binding affinity (Kd) and receptor density (R) for 125I-labeled alpha-rANP in isolated glomeruli and IMCT were Kd = 3.2 and 21 X 10(-9) M, and R = 320 and 420 fmol/mg protein, respectively. These observations suggest that alpha-rANP has a physiological action on glomeruli and possibly on the inner medullary collecting tubules in addition to the renal artery.

Animals↗
PubMed1986

Intrarenal localization of receptors for alpha-rat atrial natriuretic polypeptide: an autoradiographic study with [125I]-labeled ligand injected in vivo into the rat aorta.

We examined intrarenal localization of receptors for alpha-rat atrial natriuretic polypeptide (alpha-rANP) by injecting [125I]-labeled ligand in vivo into the rat aorta. We found that the receptors for alpha-rANP are distributed also on the vasa recta of the outer and inner medulla in addition to the previously reported sites, i.e., the renal arteries, renal pelvis, glomeruli, and inner medullary tissues including collecting tubules. In the vascular bundle of the outer medulla, the majority of grains was preferentially localized on the arterial vasa recta. The electron microscopic autoradiography of the glomerulus showed that the binding sites were mainly localized on the foot process of the podocyte. Since alpha-rANP injected into the aorta under physiological conditions was bound to the glomerulus and vasa recta in the kidney, the effect of ANP on these binding sites may be important in the mechanism of natriuresis.

Animals↗
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↗
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↗