Renal dopamine and the tubular handling of sodium.
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Animals↗
Biomedical subjects
I W Henderson
Publications and source records attributed to I W Henderson.
Interactions of atrial natriuretic peptide with A7r5 cells.
The interactions of Atrial Natriuretic Peptide with its receptors were investigated with the vascular smooth muscle cells from the A7r5 cell line. Displacement experiments of [125I]rat-Atrial Natriuretic Peptide by rat-Atrial Natriuretic Peptide revealed a single class of receptors with a Kd = 0.21 +/- 0.08 nM and a Bmax = of 35 +/- 16 fmol/mg of protein. Furthermore, the complex [125I]r-Atrial Natriuretic Peptide was internalised by a heatsensitive process. Finally, Atrial Natriuretic Peptide increased cyclic Guanosyl 3',5' Mono Phosphate in a time dependent and dose dependent way, a concentration of 0.1 microM increasing cyclic Guanosyl 3',5' Mono Phosphate level by a factor of 8.3 times when compared to basal level.
1-Methyl-3-isobutylxanthine↗
Angiotensin(1-7) is an antagonist at the type 1 angiotensin II receptor.
OBJECTIVE: The present study investigated the antagonism of the amino-terminal heptapeptide fragment of angiotensin II ([des-Phe8]-angiotensin II; Ang(1-7)) to angiotensin II (Ang II) both in vitro in rabbit aortae and in vivo in rats. METHODS AND RESULTS: In rabbit isolated endothelium intact aortic rings Ang(1-7) caused a concentration-related rightward displacement of the Ang II curve and depressed the maximum response to Ang II. By applying the data to a Schild plot an apparent pA2 of 5.5 was calculated. This depression of maximum response could be reversed by co-incubation of Ang(1-7) with the competitive angiotensin antagonist losartan. Ang(1-7) had no effect on the contractile responses of several other agonists. Intravenous infusion of 10 or 100 micrograms/kg per min Ang(1-7) had no effect on the resting blood pressure in the anaesthetized rat but inhibited Ang II-induced pressor responses. CONCLUSION: The present results show that Ang(1-7) is a specific non-competitive antagonist of Ang II at type 1 angiotensin II receptors.
Angiotensin I↗
Atrial natriuretic peptide in the Milan hypertensive rat and the Milan normotensive rat: plasma concentration and binding to renal glomeruli in young, adult and aged rats.
METHODS: Blood pressures were determined in Milan hypertensive (MHS) and Milan normotensive (MNS) rats at different ages. Mean blood pressure, plasma atrial natriuretic peptide (ANP) concentration and renal glomerular receptors numbers and affinities were determined in young (25-day-old), adult (60- to 80-day-old) and aged (300-day-old) rats. RESULTS: Mean blood pressures, always higher in the MHS than in the MNS rats, increased with age in both strains. Plasma ANP concentrations were similar in the young and aged rats of both strains, but were higher in the adult MHS than in the adult MNS rats. There were no quantitative differences in the ANP receptors between young and old rats of the two strains, but an increase in the maximal binding capacity was observed, in both strains, when adult rats were compared with young rats. Moreover, saturation experiments with [125I]-rat ANP revealed a downregulation of the ANP receptors in the renal glomeruli isolated from the adult MHS rats. In isolated glomeruli the cyclic GMP stimulation by ANP was similar in adult rats of both strains. CONCLUSION: Downregulation in glomeruli of MHS rats, probably involving the clearance receptors for ANP, is concluded to occur.
Aging↗
Renin and angiotensin converting enzyme in elasmobranchs.
Renin-like activity (RLA) and angiotensin I converting enzyme-like activity (ACELA), the two key enzymes of the renin-angiotensin system (RAS), were sought in the elasmobranch Scyliorhinus canicula. Renal extracts were desalted in a G-25 and eluted in a G-100 Sephadex column (calibration 15,000-70,000). The fractions were concentrated in a vacuum device. A 48,000-MW fraction incubated with synthetic and porcine angiotensiongen generated angiotensin I estimated by RIA. This same fraction was vasopressor in rats and dogfish. ACELA was sought in gill, heart, liver, spleen, pancreas, intestine, kidney, gonads, brain, skin, and muscle of dogfish using a spectrophotometric assay. The highest level of ACELA was found in the gills followed by spleen, kidney, and brain (33.79 +/- 2.3, 29.56 +/- 1.0, 14.62 +/- 1.0, and 13.80 +/- 2.3 nmol hippurate/min/mg protein, respectively). Intestine, gonads, skin and muscle contained no measurable amounts of ACELA. Captopril inhibited enzymatic activity from all ACELA containing tissues.
Animals↗
Atrial natriuretic peptide in the eel, Anguilla anguilla L.: its cardiac distribution, receptors and actions on isolated branchial cells.
The presence of atrial natriuretic peptide (ANP) and the nature of its binding sites were studied in fresh-water (FW)- and seawater (SW)-adapted eels using a heterologous analogue, that of the rat (rANP). Rat ANP-like immunoreactivity was demonstrated in the cardiac atria and ventricles of both FW and SW eels, and electron-dense ANP-like granules were observed. The atria and ventricles of FW eels contained significantly more granules than those of SW animals and, in both types, the atria were more granular than the ventricles. Specific binding sites for rANP were demonstrated by displacement and uptake experiments using labelled rANP in dispersed eel branchial cell preparations, enriched in chloride cells. The concentration of rANP required to produce a 50% inhibition of binding in FW cells was significantly lower than that in SW cells. Scatchard analyses revealed the presence of two classes of binding site in SW eel branchial cells but only a single class of receptor in FW cells. The affinity of the FW receptor was not significantly different from that of the SW high affinity site. Rat ANP stimulated the production of cyclic GMP (cGMP) in a dose-dependent manner, and both basal and stimulated levels of cGMP were significantly greater in SW branchial cells. These studies suggest that ANP is involved in the adaptation of the euryhaline eel to differing environmental salinities; the levels of the peptide in the heart alter with changing salinity, and the nature of the receptors in the sodium chloride-transporting epithelium of the gill changes in response to the need either to eliminate or to absorb sodium chloride.
Adaptation, Physiological↗
Characterization of a kallidin receptor in the eel intestine.
Edman degradation of an eel bradykinin (BK) -like peptide isolated and detected by gel filtration and HPLC and RIA gave an amino acid sequence of Arg1-Pro-Pro-Gly-X-Ser-Pro-Leu-Arg9. Kallidin but not BK and des-Arg9-BK contracted eel intestine. The contractile effect of kallidin was not decreased by B1 and B2 receptor antagonists (up to 10(-6)M), nor by anticholinergics, antiadrenergics, ganglion blockers and an angiotensin II receptor antagonist but was attenuated by 10(-5)M indomethacin. Kallidin appears to interact with a receptor different from the BK B1 and B2 receptor types and prostaglandins may participate in the response.
Amino Acid Sequence↗
Trans-thoracic fluid shifts and endocrine responses to 6 degrees head-down tilt.
A tomographic method of measuring electrical impedance known as Applied Potential Tomography (APT) has been used to image the impedance changes within the thoraxes of 8 healthy volunteers (4 male, 4 female) during 4-h periods of 6 degrees head-down tilt (HDT). A large decrease in impedance, reflecting an increase in thoracic fluid, was apparent within 1 min of tilting, peaked after 45 min, and was maintained throughout, although during the 4 h there was an 8% return towards baseline resistivity. Resistivity changes were most obvious in the region of the lungs. Simultaneous measurements of the key fluid regulating hormones revealed a significant increase in atrial natriuretic peptide (ANP) and a significant decrease in angiotensin II (AII) and aldosterone. There was no significant difference in plasma antidiuretic hormone level. These results illustrate the dynamic nature of fluid shifts during HDT, the spatial distribution of the fluid within the thorax and the associated endocrine responses.
Adult↗
Analysis of the renin gene intron A tandem repeat region of Milan and Lyon hypertensive rat strains.
The region of intron A of the rat renin gene containing a unique tandemly repeated sequence was analysed in the Milan and Lyon hypertensive rat strains and their controls, and in several Sprague-Dawley rats, using an oligonucleotide probe complementary to the tandemly repeated sequence and a renin complementary DNA probe. In the Milan rats, the size of the Bgl II DNA fragment encompassing the tandem repeat region was the same in the hypertensive (MHS) and normotensive (MNS) strains. In the Lyon model, a difference of 1.1 kilobase (equivalent to about 28 copies of the 38 basepair tandem repeat sequence) was observed in the size of the Bgl II fragment of the hypertensive (LH) and normotensive (LN) strains. However, the finding that the size of the fragment in the Lyon low-blood-pressure (LL) strain was the same as that in the LH strain rather than the LN strain suggests that the difference between the two latter strains is not by itself a major cause of the blood pressure difference between them in the intron A tandem region. An analysis of Sprague-Dawley rats, from which the Lyon strains are derived, showed that at least three different renin gene alleles, two with Bgl II fragments of the same size as those seen in the Lyon strains, are randomly segregating in this population.
Alleles↗
Secretory patterns of 1 alpha-hydroxycorticosterone in the isolated perifused interrenal gland of the dogfish, Scyliorhinus canicula.
An isolated in-vitro perifused interrenal gland preparation from the dogfish Scyliorhinus canicula was used to study production of quantitatively the major corticosteroid 1 alpha-hydroxycorticosterone (1 alpha-OH-B), measured by radioimmunoassay. Basal secretory rates were 877.1 +/- 145 (S.E.M.) fmol/mg per 15 min (n = 14) and the preparation remained viable for up to 22 h, as reflected in a brisk response to 10 microM cyclic AMP (cAMP) after this time. Steroid production responded in a dose-dependent manner to porcine ACTH, with 10 microM producing a maximum stimulation of 225% above the basal secretory rate. cAMP (10 microM) produced an increase of 278% above basal, while 1 microM forskolin increased basal secretory rates by 127%. [Val5]- and [Ile5]-angiotensin II (0.1 microM) increased 1 alpha-OH-B production by 120 and 372% respectively over basal secretory rates. Increasing the concentration of K+ in the perfusate from 8 mM to 12, 18, 28 and 40 mM produced a significant rise only at 28 mM. Alterations in the concentration of Na+ and osmolarity of the perifusion medium had inconsistent effects on steroid production. Increased concentrations of urea (from 360 to 720 mM) increased the basal secretory rate by 121%, whilst reducing the concentration of urea (from 360 to 90 mM) had no effect.
Adrenocorticotropic Hormone↗
Effects of altered dietary sodium intake on hormonal profiles in salt-sensitive hypertensive rats.
Blood pressure and selected putatively influential hormones were measured in Brattleboro rats which were without diabetes insipidus and which were subjected to various manipulations in dietary sodium intake. Rats fed a control diet from weaning to 16 weeks of age showed a slow increase in blood pressure whereas rats fed a sodium-enriched diet for the same period exhibited sustained hypertension (115 +/- 3 versus 169 +/- 5 (S.E.M.) mmHg). In animals fed a sodium-enriched diet plasma concentrations of antidiuretic hormone (ADH) were significantly increased from 55 +/- 8 to 108 +/- 5 fmol/l. Rats fed the control diet from weaning (group A) and subsequently maintained on that diet or changed to a sodium-enriched diet or sodium-deficient diet showed no differences in their blood pressure. Plasma hormone concentrations were similar in these groups, with the exception of aldosterone suppression in rats switched from control to a sodium-enriched diet (0.26 +/- 0.04 versus 0.08 +/- 0.03 nmol/l; P less than 0.001). Animals fed the sodium-enriched diet from weaning to 16 weeks of age (group b) and either maintained on that diet or changed to a control diet showed little change in their established hypertension. Transfer to the control diet was associated with increased plasma renin concentrations (PRC) (13.8 +/- 2.1 to 122.6 +/- 6.2 nmol/l) and plasma aldosterone concentrations (0.04 +/- 0.01 to 0.08 +/- 0.01 nmol/l; P less than 0.001) but corticosteroids and ADH concentrations were unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)
Aldosterone↗
Somatostatin-related and glucagon-related peptides with unusual structural features from the European eel (Anguilla anguilla).
Peptides derived from prosomatostatins I and II and from two distinct proglucagons have been isolated from the pancreas of a teleost fish, the European eel (Anguilla anguilla). The product of prosomatostatin I processing, somatostatin-14, is identical to mammalian somatostatin-14. A 25-amino-acid-residue peptide (Ser-Val-Asp-Asn-Gln5-Gln-Gly-Arg-Glu-Arg10-Lys-Ala-Gly-Cys- Lys15-Asn-Phe-Tyr- Trp-Lys20-Gly-Pro-Thr-Ser-Cys25) is derived from prosomatostatin II. Compared with the corresponding peptides from other teleost fish, the eel somatostatin-25 contains the unusual substitution Pro for Phe at position 22. This peptide was also isolated in a form containing a hydroxylsyl residue at position 20. A 29-amino-acid-residue eel glucagon contains four substitutions relative to human glucagon Asn for Ser8, Glu for Asp15, Thr for Ser16, and Ser for Thr29). In common with mammalian and avian glucagons but unlike most other fish glucagons, the eel peptide possesses a glutamine residue at position 3. A peptide derived from a second proglucagon comprises 36 amino acid residues. A 7-residue C-terminal extension to the glucagon sequence shows structural similarity to the corresponding extension in ratfish (Hydrolagus colliei) glucagon and mammalian oxyntomodulin.
Amino Acid Sequence↗
Influence of an enriched dietary sodium chloride regime during gestation and suckling and post-natally on the ontogeny of hypertension in the rat.
Brattleboro rats without diabetes insipidus were subjected to sodium chloride enrichment (20-fold increase in dietary salt) at various stages of their development. Salt supplementation in the adult rat produced higher systolic blood pressure (SBP), particularly in males (142 +/- 3 versus 110 +/- 3 mmHg in control. The blood pressures of females on salt-supplemented diets during pregnancy decreased from 136 +/- 1 to 121 +/- 2 mmHg, although throughout this period the blood pressures for these rats were greater than for the control pregnant rats. Pregnant females on salt-supplemented diets also showed higher sodium concentrations in the amniotic fluid compared with controls (155 +/- 3.4 versus 134.1 +/- 6.0 mmol/l). Salt supplemented lactating mothers produced milk with similar sodium concentrations to those of the controls, but the urinary sodium concentrations of pups suckling on the former were greater than in the controls. It is concluded that the suckling pups were also salt-enriched. Rats were submitted to salt-enriched regimes in utero, during suckling, post-weaning and post-pubertally, or permutations thereof. Salt supplementation post-weaning led to consistent elevation in arterial blood pressure with males being more susceptible than females. The degree of elevation was increased if the salt-supplement was present during suckling (132 +/- 1 versus 112 +/- 1 mmHg) and was greatest when the salt-supplemented regime was administered both in utero and during the post-weaning period (154 +/- 2 versus 112 +/- 1 mmHg).(ABSTRACT TRUNCATED AT 250 WORDS)
18-Hydroxydesoxycorticosterone↗
Arginine vasotocin binding to isolated branchial cells of the eel: effect of salinity.
Binding of 125I-labelled arginine vasotocin (AVT) was studied in isolated intact gill cells obtained from eels (Anguilla anguilla) adapted to fresh water (FW) or to sea water (SW). Experiments carried out at 20 degrees C showed maximum and stable binding beyond 10 min of incubation. Specific binding, determined by using labelled peptide in the presence or absence of an excess of unlabelled hormone, represented 30-50% of total and was reversible, with a half-time of less than 5 min. Scatchard plot analysis revealed the presence of a single population of saturable, high-affinity sites. Maximum binding capacity (Bmax: fmol AVT/10(6) cells) and dissociation constant (Kd: nM) were respectively 5.16 and 3.21 in FW and 24.25 and 1.05 in SW. Analysis of chloride cell number and size in gills and of binding characteristics of AVT revealed parallel changes with external salinity. These results are taken as evidence for the direct intervention of neurohypophysial peptides on the gill epithelium of teleost fishes.
Animals↗
Gastrin-releasing peptide from the intestine of the elasmobranch fish, Scyliorhinus canicula (common dogfish).
The concentration of gastrin-releasing peptide in the intestine of the elasmobranchian fish, Scyliorhinus canicula, measured with an antiserum directed against the COOH-terminal region of porcine gastrin-releasing peptide, was higher than the concentrations measured in mammalian intestines. The immunoreactivity was resolved by gel permeation chromatography into two peaks with the approximate elution volumes of porcine gastrin-releasing peptide and bombesin/neuromedin C. The primary structure of the larger peptide was established as Ala Pro Val Glu Asn Gln Gly Ser Phe Pro Lys Met Phe Pro Arg Ser His (Trp) Ala Val Gly (His Leu Met.NH2). Residues in parentheses are only tentatively assigned. Chromatographic evidence and the presence of the arginyl residue at position 15 in the peptide suggest that the smaller molecular form of gastrin-releasing peptide may be identical to mammalian neuromedin C. Amphibian bombesin was not identified in the dogfish gut.
Animals↗
Water uptake by Rana temporaria: effects of diuretics and the renin--angiotensin system, and nephrectomy.
Adult Rana temporaria, acclimated to tap water or hyperosmotic (0.9% NaCl saline) media, were injected with Acetazolamide, Frusemide, or Captopril, or were nephrectomized and injected with captopril. Saline-injected animals served as controls. Total water flux and drinking rates were determined by body weight changes and by the rate of accumulation of an environmental marker (phenol red) in the gut, respectively. Changes in plasma corticosteroids and ion concentrations were also assessed. Acetazolamide and frusemide produced hyponatraemia in tap water-acclimated animals, but induced increased aldosterone levels in frogs in both environments. Captopril reduced body weight and aldosterone levels of tap water frogs, but had no effect on plasma ion composition. Animals treated with captopril on immersion in saline had plasma hypoosmotic to their environment. Saline-acclimated frogs drank less environmental water than did those in tap water. Captopril, acetazolamide, and frusemide all stimulated drinking rates of saline-acclimated frogs; captopril, however, had no effect on the drinking rates of nephrectomized animals, indicating that the dipsogenic actions of this drug are probably reflected by inhibition of the renin-angiotensin system. In tap water animals, acetazolamide stimulated drinking, while frusemide stimulated integumental water uptake. No correlation was apparent between plasma aldosterone and corticosterone concentrations, or between changes in body weight and drinking rates. This suggests that there are independent mechanisms controlling aldosterone and corticosterone secretion, as well as integumentary and buccal uptake of water in R. temporaria.
Acetazolamide↗
The expanding endocrine system.
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Animals↗
Metabolism of 25-hydroxycholecalciferol in a teleost fish, the rainbow trout (Salmo gairdneri).
Plasma concentrations of vitamin D3 (cholecalciferol) metabolites have been studied in rainbow trout (Salmo gairdneri) adapted to varying environmental calcium concentrations in both fresh water and artificial seawater, and in natural seawater. In vivo, intraarterial injection of tritiated 25-hydroxycholecalciferol was followed by its transformation to a number of metabolites including compounds that cochromatographed on high performance liquid chromatography (HPLC) with 1,25-dihydroxycholecalciferol and 25,26-dihydroxycholecalciferol. Hypercalcaemia and increased environmental calcium were associated with a greater transformation to the compound cochromatographing with 25,26-dihydroxycholecalciferol, while hypocalcaemia and reduced environmental calcium concentrations induced more conversion to the 1,25-dihydroxycholecalciferol-like compound. In vitro, both metabolites were produced by liver but not by kidney preparations, and the difference in conversion ratios observed in vivo associated with changes in plasma calcium were also seen in vitro. It is concluded that the metabolism of 25-hydroxycholecalciferol in the trout can be influenced by calcium status, but at present the physiological importance of this metabolism and the mechanisms and site(s) of action of the metabolites are unknown.
Animals↗