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Biomedical subjects

T Inagami

Publications and source records attributed to T Inagami.

At least 307 records · Page 17Linked to original sources
PubMed1987

Multiple forms of immunoreactive renin in human adrenocortical tumour tissue from patients with primary aldosteronism.

There is increasing evidence which suggests that the adrenal gland contains the renin-angiotensin cycle. The localization of renin has been reported to be mainly in the zona glomerulosa rather than the fasciculata medullary portion. In the present study we have investigated extracts from aldosteronomas (n = 3), which are believed to derive from the zona glomerulosa cells. In addition, we have attempted to characterize the biochemical properties of the adrenal renin. Sizable quantities of renin-like activity (32.0 +/- 7.7 ng of angiotensin I generated h-1 mg-1 of protein, mean +/- SEM) were detected in the extracts. This renin-like activity was inhibited by anti-renin antibody raised against pure renin (mean, 95% of the total renin-like activity), indicating that it was not due to the non-specific action of proteases such as cathepsin D. The optimum pH of the tissue renin-like enzyme was 6.0 for rat plasma substrate. Differences were found, however, in the molecular mass (36,000, 37,000, 44,000 and 48,000), binding to concanavalin A and isoelectric points (4.40, 4.68 and 5.00). These results confirm the existence of specific renin in aldosteronoma. Renin microheterogeneity could be evidence for local production of the enzyme.

Adrenal Cortex Neoplasms↗
PubMed1987

A search for endogenous Na+,K+-ATPase inhibitor in acutely volume-expanded hog plasma led to lysophosphatidylcholine gamma-stearoyl.

An Na+,K+-ATPase inhibitor possessing inhibitory activity against the specific binding of ouabain to Na+,K+-ATPase has been purified from the plasma of acutely saline-infused hogs. The purification was performed by a combination of Amberlite XAD-2 adsorption chromatography and five steps of high-pressure liquid chromatography (HPLC). Fast atom bombardment mass and proton nuclear magnetic resonance (NMR) spectrometric studies identified the purified substance as lysophosphatidylcholine gamma-stearoyl (LPCS). The ouabain-displacing activity in plasma, due to this compound, increased with time during saline infusion. The maximal level reached was approximately 12 times higher than that in the pre-infusion plasma sample. Lysophosphatidylcholines (LPCs) containing myristoyl, palmitoyl and oleoyl groups were also inhibitory to Na+,K+-ATPase and ouabain-binding to the enzyme. These LPCs were effective at 100 mumol/l concentrations in attaining 50% inhibition of the enzyme activity and ouabain-binding activity of Na+,K+-ATPase. These results suggest that LPCs containing long chain fatty acids could play an important role as a Na+,K+-ATPase inhibitors under volume-expanded conditions.

Animals↗
PubMed1987

Postural suppression of plasma atrial natriuretic polypeptide concentrations in man.

The effects of sequential changes in posture, from recumbency, to sitting and then to the upright position, each for 60 min, respectively, on the levels of plasma immunoreactive atrial natriuretic polypeptide (ANP) in healthy human subjects were studied using a radioimmunoassay (RIA) method. At the end of each change in posture, plasma ANP levels were respectively 150 +/- 16.4 pg/ml (recumbent), 103 +/- 11.2 pg/ml (sitting), and 78.1 +/- 7.90 pg/ml (upright). In contrast, plasma renin concentration (PRC) and plasma aldosterone concentration (PAC) determined concomitantly with ANP showed a significant increase in response to the sitting and upright postures. Plasma ANP levels determined in normal subjects who remained in the recumbent posture for the same period did not show any significant change. This suggests that ANP is involved in the maintenance of haemodynamic homeostasis under physiological conditions and emphasizes that postural factors must be taken into account and controlled in order to evaluate plasma ANP levels properly, as well as those of PRC and PAC.

Adult↗
PubMed1987

Identification of atrial natriuretic factor receptor of neuroblastoma N4TG1 cells: binding characteristics and photoaffinity labeling.

We have found specific receptors for atrial natriuretic factor (ANF) in cultured neuroblastoma cells (N4TG1) of peripheral ganglionic origin. Scatchard analysis of the displacement binding revealed noninteracting, single-class binding sites with a KD of 1 X 10(-10) M and a density (Bmax) of 110,000-150,000 sites/cell. The cell-bound 125I-ANF was displaced by unlabeled ANF in a dose-dependent manner. Hormones unrelated to ANF such as angiotensins, adrenocorticotropic hormone, or arginine vasopressin were ineffective in displacing the cell-bound radioactivity. Using azidobenzoyl-125I-ANF as a photoaffinity ligand, an ANF receptor with an apparent Mr of 138,000 was identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. The addition of unlabeled ANF (1 microM) to the incubation medium completely abolished the labeling of this protein band, but atriopeptin I (1 microM) or angiotensins I, II, and III (each 1 microM) were not effective in inhibiting the affinity labeling. The treatment of the neuroblastoma cells with ANF stimulated intracellular cyclic GMP levels in a dose-dependent manner with an EC50 of 5 nM. ANF (1 X 10(-7) M) stimulated cyclic GMP accumulation in less than 5 min by 30-fold as compared to the controls.

Affinity Labels↗
PubMed1987

Atrial natriuretic peptide, right atrial pressure, and sodium excretion rate in the rat.

This study examined the relationship between right atrial pressure (RAP), urine flow rate, sodium excretion rate, and plasma atrial natriuretic peptide (ANP) levels after an acute Ringer expansion. Two groups of rats had their RAP monitored and balloon catheters placed in their thoracic inferior venae cavae. In one group the balloon remained deflated, and in the second group the balloon was inflated during the volume expansion in an attempt to prevent the rise in RAP. The peak RAP was 7.3 +/- 0.8 mmHg when the balloon remained deflated and 3.5 +/- 0.6 mmHg in the group with the balloon catheter inflated (P less than 0.005). The corresponding peak ANP levels were 682 +/- 140 and 223 +/- 40 pg/ml. There was a significant correlation between the peak RAP and ANP levels (r = 0.754; P less than 0.05). The inflation of the balloon catheter significantly decreased the urine flow rate and the urine sodium excretion rate. A final group of animals had 200 microliters of rabbit serum containing antibody to ANP infused before the volume expansion. The antibody-treated animals had significantly lower urine flow and sodium excretion rates than nonantibody-treated control rats. We conclude that ANP is one of the factors which allows the rat to excrete an acute Ringer expansion.

Animals↗
PubMed1987

Isolation of renin-rich rat kidney cells.

Enzymatic dispersion and density gradient (Percoll) sedimentation were used to isolate a population of renin-containing, granule-laden cells (density 1.067 g/ml) from rat kidney cortex. Using immunohistochemistry (light microscopy) and electron microscopy, we defined the presence and ability of these cells to store renin protein(s). A 1000 base pair rat renin complementary DNA was used to show that these cells express the renin gene. The reverse hemolytic plaque assay defined the functional properties of the renin-containing cell. The data are consistent with the postulated inverse relationship between calcium concentration and release of renin. Thus, we have isolated a population of functional rat kidney cells that synthesize, store, and release renin.

Animals↗
PubMed1987

Identification of Na+,K+-ATPase inhibitors of volume-expanded hog plasma.

Na+,K+-adenosine triphosphatase (ATPase) inhibitors possessing inhibitory activities against the specific binding of ouabain to Na+,K+-ATPase and 86Rb uptake into hog erythrocytes have been purified from the plasma of hog acutely infused with saline. The purifications were performed by a combination of Amberlite XAD-2 adsorption chromatography and several steps of high performance liquid chromatography using four different types of columns. Inhibitors purified to homogeneity were identified as linoleic and oleic acids, gamma-stearoyllysophosphatidylcholine, gamma-arachidoyllysophosphatidylcholine, gamma-linoleoyllysophosphatidylcholine, and gamma-oleoyllysophosphatidylcholine. Small amounts of beta-arachidoyllysophosphatidylcholine, gamma-docosapentaenoyllysophosphatidylcholine, gamma-eicosatrienoyllysophosphatidylcholine, and gamma-palmitoyllysophosphatidylcholine were also detected by both fast atom bombardment mass and proton nuclear magnetic resonance spectrometric studies. Only gamma-acyllysophosphatidylcholines showed inhibitory activities on Na+,K+-ATPase and ouabain-binding activities. These lysophosphatidylcholines and unsaturated free fatty acids were effective at 100 microM levels in attaining 50% inhibition of the enzyme activity. The ouabain-displacing activity in plasma caused by these compounds increased with time during saline infusion. The maximal plasma levels of these components were approximately 10 times higher than that in the preinfusion plasma sample.

Animals↗
PubMed1987

Structure and physiological actions of rat atrial natriuretic factor.

Natriuretic substances were purified from rat atrium (atrial natriuretic factor, ANF) and were shown to be identical with the inhibitor of norepinephrine-induced contraction of smooth muscle. Four native forms were isolated and their amino acid sequences were determined. The presence of a high-molecular-weight prohormone was shown. Complementary DNA (cDNA) encoding for the precursor was cloned and used to deduce the amino acid sequence of the prohormone. Genomic DNA for ANF was cloned and two introns were found. Several ANF peptides were synthesized. Structure-function studies showed that the ring structure was essential for the activity. Antibodies produced against the synthetic 25-amino acid residue ANF were used to develop a radioimmunoassay. The presence of ANF in rat plasma demonstrated that ANF is a circulating hormone. ANF was also found in the hypothalamus of rats. The ANF in plasma was found to be a low-molecular form, whereas that in atria and hypothalamus consisted of both the high-molecular-weight precursor and low-molecular-weight active ANF. The presence of messenger RNA for ANF was determined using ANF cDNA as a probe and was considered as evidence for ANF synthesis in the brain, atrium, and ventricles. ANF was shown to be released from the brain. ANF administered intracerebroventricularly was shown to inhibit angiotensin II and thirst-induced dipsogenesis. In vitro and in vivo experiments showed ANF inhibits release of vasopressin from posterior pituitary and renin from the kidneys. The hypotensive effect of ANF was examined at various doses.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1987

Specific receptor-mediated stimulation of progesterone secretion and cGMP accumulation by rat atrial natriuretic factor in cultured human granulosa-lutein (G-L) cells.

The effect of rat atrial natriuretic factor (ANFIV102-126) on the regulation of steroidogenesis in human G-L cells have been studied in vitro. The treatment of cells with ANF (1 X 10(-8)M) resulted in a 3- to 4-fold increase in progesterone secretion compared to the controls. ANF in combination with LH (200 ng/ml) increased progesterone secretion more than six-fold over controls. Concomitantly, ANF stimulated the accumulation of cGMP 30-fold, whereas the level of cAMP was either unchanged or fell slightly (10-15%). Mono[125I]-iodo-ANF bound to G-L cell surface specific receptors with a Kd of 1.8 X 10(-10)M at a density (Bmax) of 160,000-190,000 sites/cell. The binding of [125I]-iodo-ANF was competed by unlabeled ANF in a dose-dependent manner, and hormones unrelated to ANF, such as angiotensins, ACTH or LH, were unable to compete with [125I]-iodo-ANF. The results indicate that ANF can stimulate progesterone secretion and cGMP accumulation in ovarian G-L cells without affecting the level of cAMP and that the stimulatory effects of ANF on G-L cell steroidogenesis may proceed via mechanism(s) involving an intracellular messenger other than cAMP.

Animals↗
PubMed1987

Atrial natriuretic polypeptide inhibits cortisol secretion as well as aldosterone secretion in vitro from human adrenal tissue.

The effect of alpha-human atrial natriuretic polypeptide (ANP) on adrenal steroidogenesis was studied in human adrenal tissues obtained surgically from four patients with Cushing's syndrome due to an adrenal adenoma and five patients with an aldosterone-producing adenoma (APA). ANP significantly inhibited basal and ACTH (3.4 X 10(-8) M)-stimulated cortisol and aldosterone secretion in both the adenomas and adjacent adrenocortical tissues from patients with Cushing's syndrome. ANP inhibited ACTH-stimulated, but not basal, secretion of cortisol and aldosterone in the adjacent tissues from patients with APA. In addition, ANP significantly inhibited both basal and ACTH-, angiotensin II (10(-6) M)-, and potassium chloride (10 mM)-stimulated secretion of aldosterone from the adenomas of patients with APA. ANP-induced changes in cortisol and aldosterone secretion were accompanied by a decrease in cAMP and an increase in cGMP secretion. These results suggest that ANP may be a possible regulator of cortisol as well as aldosterone secretion in humans, and these effects might be due to concomitant alteration in cyclic nucleotide metabolism.

Adenoma↗
PubMed1987

Atrial natriuretic factor is biologically active also in the absence of vasopressin: studies on Brattleboro-strain diabetes insipidus rats.

Since atrial natriuretic factor (ANF) has been shown to inhibit vasopressin secretion, the role of this effect in the acute biological actions of ANF was investigated using Brattleboro-strain diabetes insipidus (DI) rats. Under thiobarbital anesthesia, synthetic rat ANF of a 25 amino acid sequence was administered intravenously as a bolus (8 micrograms/kg) into the jugular vein. The urine volume, urinary sodium and potassium concentration, blood pressure, and heart rate were determined. It was found that ANF administered exogenously can exhibit its diuretic, natriuretic and vasorelaxant activities even in the absence of vasopressin. This indicates that the inhibition of vasopressin secretion is not an indispensible mechanism for acute biological effects of ANF.

Animals↗
PubMed1987

Effect of captopril on angiotensin II release from vascular tissues in rats.

Isolated rat hindlegs were perfused with Krebs-Ringer solution and released angiotensin I (ANG I) and ANG II were determined. The release of ANG I and ANG II in nephrectomized rats did not differ from those in control group. Pretreatment with captopril (50 mg/kg/day) for 3 days or addition of captopril (2 X 10(-6) M) to the perfusate induced increase in ANG I release and decrease in ANG II release. These findings suggest that ANG II is locally generated and release from the vascular tissues. Captopril may inhibit the conversion of vascular ANG I into ANG II.

Angiotensin I↗
PubMed1987

Immunohistochemical localization of renin in renal tumors.

Immunoperoxidase staining for renin was performed with renal tumors, including juxtaglomerular (JG) tumor, Wilms' tumors, renal adenocarcinomas, renal oncocytomas, and cortical adenomas. Compared with the JG apparatus adjacent to the glomerulus, JG tumor cells were less darkly but diffusely stained for renin. One of five Wilms' tumors revealed more numerous renin-containing tumor cells than the adjacent renal cortex, whereas three of ten renal adenocarcinomas and two of three renal oncocytomas revealed only focally renin-positive tumor cell cytoplasms. None of six cortical adenomas were positive for renin. With available fresh tumor tissue, renin activity was studied by measuring newly formed angiotensin I by radioimmunoassay. JG tumor contained markedly elevated renin activity, whereas one Wilms' tumor and two renal adenocarcinomas contained no more than 2% of renin activity of the renal cortex, more than 50% of which was inactive renin. These findings suggest that the JG tumor elaborates enormous amounts of active renin, whereas other renal tumors produce lesser amounts of renin, more than half of which is inactive renin.

Adenocarcinoma↗
PubMed1986

Atrial natriuretic factor receptor on cultured Leydig tumor cells: ligand binding and photoaffinity labeling.

Atrial natriuretic factor (ANF) is a peptide hormone discovered recently from the heart atrium that possesses potent natriuretic and vasorelaxant activities. Recently we found that ANF markedly stimulates intracellular cGMP and almost completely inhibits cAMP accumulation in testicular interstitial tumor cells [Pandey, K. N., Kovacs, W. J., & Inagami, T. (1985) Biochem. Biophys. Res. Commun. 133, 800-806]. These actions of ANF suggest the presence of ANF receptors in testicular interstitial cells. In this study, cultured murine Leydig tumor cells have been shown to contain specific binding sites for ANF. Saturation binding studies indicated a single class of binding sites with a Kd of 5 X 10(-9) M at a density of 2 X 10(6) sites/cell. The binding of mono[125I]iodo-ANF (125I-ANF) was competed by unlabeled ANF in a dose-dependent manner. Hormones unrelated to ANF such as angiotensin I, bovine luteinizing hormone, and human chorionic gonadotropin were not able to compete against 125I-ANF. The binding of 125I-ANF was rapid, reaching maximum levels in 15 min at 4 degrees C. At 37 degrees C, the cell-bound 125I label was quickly decreased. Pretreatment of cells with NH4Cl, chloroquine, or NaN3 resulted in significant increases in maximum levels of the cell-bound 125I radioactivity. A photoaffinity reagent for ANF receptor was prepared by reacting ANF with succinimido 4-azidobenzoate, and resultant 4-azidobenzoyl- (AZB-) ANF was purified by high-performance liquid chromatography (HPLC). AZB-ANF was radioiodinated by use of chloramine T and purified again by HPLC.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Regional increase of cyclic GMP by atrial natriuretic factor in rat brain: markedly elevated response in spontaneously hypertensive rats.

Atrial natriuretic factor (ANF)-responsive areas in rat brain were examined by measuring ANF-stimulated cyclic GMP production in rat brain slice preparations. The medulla oblongata, thalamus, and pituitary gland responded most sensitively, the septum, hypothalamus, pons, midbrain and olfactory bulb responded moderately, but neocortex, cerebellum, striatum and hippocampus were unresponsive to ANF. The most responsive regions in spontaneously hypertensive rats brains showed 2 to 5 times higher cyclic GMP production than those from the control Wistar-Kyoto rats. These findings provide evidence for biological action of ANF on brain tissues, and indicate the action of ANF produced in the brain.

Animals↗
PubMed1986

Atrial natriuretic factor regulates steroidogenic responsiveness and cyclic nucleotide levels in mouse Leydig cells in vitro.

The effects of synthetic atrial natriuretic factor (ANF) on the regulation of mouse Leydig cell steroidogenesis have been studied in vitro. ANF in nanomolar concentration increased testosterone production by more than 30-fold over basal levels. Concomitantly, cyclic guanosine monophosphate levels were increased 35-fold; cyclic adenosine monophosphate levels fell minimally (15-20%). ANF at low concentration (1 X 10(-11) M) inhibited testosterone production by luteinizing hormone-stimulated cells, while at higher concentration (greater than 2 X 10(-9) M) ANF stimulated steroidogenesis beyond the level attained by luteinizing hormone alone. These results indicate that ANF can exert stimulatory effects on testosterone steroidogenesis in vitro, and that the mechanism may involve an intracellular messenger other than cyclic adenosine monophosphate.

Animals↗
PubMed1986

Atrial natriuretic factor is released from rat hypothalamus in vitro.

In vitro release of atrial natriuretic factor (ANF) from rat hypothalamic fragment during 60 min incubation was studied using a specific and sensitive radioimmunoassay (RIA). The Sephadex G-75 gel filtration profiles of the incubation medium revealed that the majority of released ANF-like immunoreactivity (LI) had a molecular weight same as alpha-atrial natriuretic polypeptide and a small amount of ANF-LI of larger molecular size was also released. The release of ANF was increased by addition of 50 mM KCl and the release by 50 mM KCl was completely suppressed in the presence of 2 mM EGTA, a chelating agent of Ca2+. A23187, a Ca2+ ionophore, at a concentration of 2 X 10(-4) M augmented the release of ANF-LI. These results indicate that hypothalamic ANF is released in a Ca2+-dependent manner like other hypothalamic peptides. This suggests that hypothalamic ANF acts as a neurotransmitter and/or neuromodulator in the hypothalamus and possesses some role in the regulation of pituitary hormone secretion.

Animals↗