Enzymatic and binding effects of atrial natriuretic factor in glomeruli and nephrons

Atrial natriuretic factor (ANF) has been suggested to exert a tubular effect on the mammalian nephron, perhaps in part by interacting with other hormones. In the present study, the effect of ANF was examined on glomeruli (Gm) and different renal tubule segments including medullary (MAL) and cortical thick ascending limb (CAL) and cortical (CCT), outer medullary (OMCT) and inner medullary collecting tubules (IMCT). This effect of ANF was assessed by alteration in adenylate cyclase and cGMP in the various nephron segments in the presence and absence of arginine vasopressin (AVP), parathyroid hormone (PTH) and calcitonin (SCT). An effect of ANF (10(-8) M) was not demonstrated on adenylate cyclase (fmol cAMP formed/30 min/micrograms protein) in Gm, CAL, MAL, CCT, OMCT or IMCT. Nor did ANF (10(-8) M) interfere with the effect of PTH (5 IU/ml) on the Gm (PTH 35.1 +/- 3.7 vs. PTH + ANF 32.5 +/- 1.8, NS), CAL (PTH 50.5 +/- 10.9 vs. PTH + ANF 46.2 +/- 1.4, NS) or AVP (10(-8) M) on the CCT (AVP 40.8 +/- 6.6 vs. AVP + ANF 33.0 +/- 3.1, NS), OMCT (AVP 56.0 +/- 11.8 vs. AVP + ANF 42.1 +/- 6.7, NS), IMCT (AVP 66.5 +/- 4.6 vs. AVP + ANF 53.5 +/- 7.0, NS) or MAL (AVP 15.5 +/- 1.6 vs. AVP + ANF 14.0 +/- 2.6, NS). ANF also did not affect SCT (1.5 x 10(-8) M)-induced adenylate cyclase on CCT (SCT 69.8 +/- 11.3 vs. SCT + ANF 79.9 +/- 7.2, NS). ANF (10(-8) M), however, significantly increased cGMP in the Gm (6.4 +/- 1.7 to 121.3 +/- 32.4 fmol/micrograms protein, P less than 0.001) and IMCT (0.63 +/- 0.16 to 1.46 +/- 0.29 fmol/micrograms protein, P less than 0.05). However, no effect of ANF on cGMP was observed in the CAL, CCT, OMCT, and MAL even at 10(-7) M ANF. PTH (5 IU/ml) did not alter either basal or ANF-stimulated cGMP in the Gm. Also, specific ANF binding was studied in the microdissected IMCT. Kd was 6.08 x 10(-9) M and Bmax was 8.07 x 10(-11) M.(ABSTRACT TRUNCATED AT 250 WORDS)

Ovine fetal response to water deprivation: aspects on the role of vasopressin

The effect of maternal hyperosmolality as created by an acute mannitol infusion was evaluated in eight chronic sheep preparations. Fetal osmotic and haemodynamic responses were compared to those achieved during an arginine vasopressin (AVP) infusion into the fetus (approximately 400 microU/(min kg]. To assess the AVP sensitivity of the fetal kidney the urine osmolality was determined. The activity of adenylate cyclase was measured in placental cotyledons as an indicator of AVP receptors affecting water permeability. The maternal mannitol infusion induced an increase in fetal serum AVP levels from 1.18 +/- 0.25 up to 13.76 +/- 2.11 pg/ml. During the fetal AVP infusion the AVP levels were approximately 22 pg/ml, somewhat higher when given concurrently with a mannitol infusion to the ewe (peak value: 26.13 +/- 2.80 pg/ml). Fetal heart rate increased significantly during maternal hyperosmolality while this effect was blunted by exogenous AVP given to the fetus. The AVP infusion did not affect fetal or maternal serum osmolality. During the mannitol infusion fetal serum osmolality increased to peak values which were not significantly different whether or not AVP was infused into the fetus (from 298.0 +/- 0.85 to 309.0 +/- 0.90, and from 297.7 +/- 1.47 to 307.9 +/- 0.90 mosmol/kg, respectively). Similarly, there were no differences in the effect of mannitol infusion upon fetal urine osmolality with or without AVP infusion (increments: + 149.7 +/- 34.12 and + 148.7 +/- 31.30 mosmol/kg, respectively). Adenylate cyclase activity in the placenta was unchanged before and after AVP stimulation. The data suggest an unresponsiveness of placental water permeability to fetal AVP infusion. We also conclude that a maximal urine osmolality was reached already at AVP levels obtained after an osmotic maternal load whereas at AVP levels more than twice as high the cardiovascular effects were still AVP dose-dependent.

AVP-induced Ca fluxes and contraction of rat glomerular mesangial cells

Arginine vasopressin (AVP) is known to exert Ca mobilization and contraction in glomerular mesangial cells and vascular smooth muscle cells. However, the relationship between changes in intracellular Ca and transmembrane Ca fluxes is not clear at the present time. Therefore, this study was undertaken to determine the effect of AVP on cytosolic calcium ([Ca2+]i) and Ca fluxes as estimated by measurements of 45Ca2+ efflux. Changes of [Ca2+]i in response to AVP were directly measured in monolayers of adherent cultured mesangial cells. AVP induced rapid concentration-dependent increases in [Ca2+]i and Ca2+ efflux. AVP also induced contraction of mesangial cells. This effect was blocked only by the V1 (pressor)-antagonist, d(CH2)5Tyr(Me)AVP. Stimulation of Ca2+ efflux and changes in [Ca2+]i by AVP completely desensitized the mesangial cells to a subsequent identical challenge of AVP with no cross-tachyphylaxis to other hormones. Even in Ca2+-free medium, AVP increased [Ca2+]i and Ca2+ efflux, but to a lesser extent. Under this condition, contraction of mesangial cells induced by AVP was also observed. Readdition of extracellular Ca2+ following the AVP-induced increase in [Ca2+]i caused a second and slower [Ca2+]i increase. In Ca2+-containing conditions, lanthanum ion-reduced AVP evoked [Ca2+]i stimulation to the value observed in Ca2+-free medium. The Ca2+ channel blocker, verapamil, partially inhibited AVP-induced Ca2+ influx but totally blocked the increase in [Ca2+]i induced by high K. Verapamil did not inhibit AVP-stimulated Ca2+ efflux and cell contraction. Dantrolene, a blocker of Ca2+ release from endoplasmic reticulum, inhibited AVP-stimulated Ca2+ efflux and cell contraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of angiotensin II on Ca2+ kinetics and contraction in cultured rat glomerular mesangial cells

This in vitro study was undertaken to determine the changes in Ca2+ kinetics and cell shape of cultured putative glomerular mesangial cells in the rat in response to angiotensin II (ANG II). Intracellular Ca2+ ([Ca2+]i) was measured using quin 2. ANG II-stimulated Ca2+ efflux was also determined. ANG II induced rapid concentration-dependent increases in [Ca2+]i and Ca2+ efflux. ANG II also induced contraction of mesangial cells as assessed by alterations in cell shape. Even in Ca2+-free medium, ANG II increased [Ca2+]i and Ca2+ efflux, but to a lesser extent. Under this condition, contraction of mesangial cells induced by ANG II was also observed. Readdition of extracellular Ca2+ after the ANG II-induced increase in [Ca2+]i caused a second and slower [Ca2+]i increase. High potassium (50 mM) induced a change of [Ca2+]i, but to a lesser extent compared with the ANG II-induced change. The Ca2+ channel blocker verapamil (5 x 10(-5) M) partially inhibited ANG II-induced Ca2+ influx but totally blocked the increase in [Ca2+]i induced by high potassium. Verapamil did not inhibit ANG II-stimulated Ca2+ efflux or the change in cell shape. Dantrolene (10(-4) M), a blocker of Ca2+ release from endoplasmic reticulum, inhibited ANG II-stimulated Ca2+ efflux and change in cell shape. These results indicate that ANG II rapidly increases [Ca2+]i in cultured rat mesangial cells, in part by mobilizing Ca2+ from dantrolene-sensitive intracellular pools and in part through activation of receptor-operated and voltage-dependent Ca2+ channels. The [Ca2+]i mobilization, however, seems to be the primary modulator of initial glomerular mesangial cell contraction.

Cellular action of arginine vasopressin in the isolated renal tubules of hypothyroid rats

Hypothyroidism has been demonstrated to be associated with an impaired concentrating capacity and specific morphological changes in the thick ascending limbs. This study was performed to evaluate the cellular action of arginine vasopressin (AVP) in the isolated renal tubules from control (C) and hypothyroid (HT) rats. Hypothyroidism was induced by feeding aminotriazole for 4 wk. Urinary volume was higher in HT rats (C 13.5 +/- 0.9, HT 17.7 +/- 0.9 ml/24 h, P less than 0.005) and urinary osmolality was lower in HT rats (C 1,707 +/- 49, HT 1,229 +/- 35 mosmol/kgH2O, P less than 0.001). Plasma AVP levels were significantly higher in HT rats (C 1.93 +/- 0.59, HT 4.12 +2- 0.62 pg/ml, P less than 0.05), thus documenting AVP resistance. The adenylate cyclase response to AVP (10(-6) M) was significantly lower (P less than 0.02) in the medullary thick ascending limb of Henle's loop (mTALH) in HT (14.3 +/- 2.4 to 41.7 +/- 5.8 fm X 30 min-1 X mm-1, P less than 0.001) than in mTALH in C rats (14.4 +/- 2.8 to 110.1 +/- 24.9 fm X 30 min-1 X mm-1, P less than 0.001). In contrast, the adenylate cyclase response to AVP was not significantly different in collecting tubules of cortex, outer medulla, and inner medulla from C and HT rats, although a slight decrease in response to AVP was observed in cortical and outer medullary collecting tubules.(ABSTRACT TRUNCATED AT 250 WORDS)

Purification of a chick brain-derived growth factor by reversed-phase high-performance liquid chromatography

A chick brain-derived growth factor (CBGF) has been purified to apparent homogeneity by a combination of ultrafiltration, DEAE ion-exchange, and reversed-phase high-performance liquid chromatography on a C18 column. CBGF has an apparent molecular mass of approximately 1500 Da. The amino acid composition of CBGF has been determined and reveals a peptide containing predominantly glycine, glutamic acid/glutamine, and aspartic acid/asparagine. This mitogen is highly active, with half-maximal stimulation of chick brain astrocytes at 5 ng/ml in an assay using incorporation of methyl-3H-thymidine into DNA. In addition to its effects on chick astrocytes, purified CBGF from the 18 d chick embryo is mitogenic for amphibian limb regeneration blastema cells in vitro. A possible role for this mitogen in the nerve-dependent regeneration of amphibian appendages is discussed.

Role of arginine vasopressin in medullary thick ascending limb on maximal urinary concentration

Two groups of Sprague-Dawley rats, Harlan (H) and Charles River (CR), were discovered in that the medullary thick ascending limb (MAL) had a profoundly different adenylate cyclase response to arginine vasopressin (AVP). Using these two groups of rats, we studied the correlation between AVP action on the MAL and maximal urinary concentration. AVP (10(-6) M) significantly stimulated adenylate cyclase in MAL of H rats (7.4 +/- 0.9 to 43.8 +/- 4.6 fmol cAMP formed X 30 min-1 X mm-1, P less than 0.001) but not in CR rats (10.3 +/- 1.4 to 12.7 +/- 2.0 fmol cAMP formed X 30 min-1 X mm-1, NS). In contrast, AVP significantly stimulated adenylate cyclase of cortical, outer and inner medullary collecting tubules from both H and CR rats. Glucagon (10(-6) M) significantly stimulated adenylate cyclase of MAL from both H and CR rats. After 48 h of fluid deprivation, urinary osmolality was significantly higher (P less than 0.001) in the H (4,504 +/- 399 mosmol/kg H2O, n = 14) than CR (2,840 +/- 176 mosmol/kg H2O, n = rats. This observation was not attributable to differences in creatinine clearance (CR, 1.30 +/- 0.24; H, 1.24 +/- 0.03 ml/min, NS, n = 4) or plasma AVP (CR, 12.75 +/- 1.44; H, 12.38 +/- 1.17 pg/ml, NS, n = 6) levels. These results therefore suggest that the action of AVP on the MAL, in addition to the effect on collecting tubules, is involved in maximal urinary concentration in rats.

Purification of murine erythropoietin produced in serum-free cultures of erythroleukemia cells

We previously documented that several erythroleukemia cell lines released factors that stimulated erythropoiesis in vivo and in vitro. A simple five-step scheme has been devised that allows purification of this erythropoietic activity to apparent homogeneity. The methods employed included lectin affinity chromatography (wheat germ agglutinin), gel filtration (ultro gel ACA44), ion exchange, hydroxylapatite, and high performance liquid chromatography. Following polyacrylamide gel electrophoresis, biologic activity was recovered in an area corresponding to a molecular weight of 35,000 daltons. Silver staining of a polyacrylamide gel after electrophoresis of our most purified preparation revealed a single band at 35,000 daltons.

Recognition and recall in amnesics

Although there is considerable agreement that performance in direct memory tasks (e.g., recall, recognition) is more disrupted by amnesia than performance in indirect memory tasks (e.g., mirror reading, word completion), one may be able to further circumscribe the deficit within the domain of direct memory tasks. The present article explores whether recall is disproportionately disrupted by amnesia compared to recognition. If amnesia affects memory uniformly across different direct memory measures, recall of normal controls should not differ from the recall of amnesics when recognition scores of these two groups are equated. On the other hand, if recall is disproportionately disrupted, normal recall should be superior to amnesic recall even when recognition is equated. The present study equated amnesic recognition with that of controls by providing amnesics with 8 s of study time and normal subjects with 0.5 s. Amnesics with Korsakoff's syndrome, amnesics with other etiologies, and appropriate controls were examined. Normal recall was superior to amnesic recall even when no differences were found in recognition. The results further specify the selective nature of amnesia.

Effect of trifluoperazine on rabbit cortical collecting tubular response to vasopressin

Anuran membrane studies suggest that the calcium-binding protein calmodulin is necessary for arginine vasopressin (AVP) to exert a hydro-osmotic effect. We therefore examined the effect of trifluoperazine and N-(6-aminohexyl)-5-chloro-1-naphtholene sulphonamide (W-7), chemically dissimilar calmodulin inhibitors, on hydraulic conductivity (Lp) response to AVP in rabbit cortical collecting tubules perfused in vitro. Trifluoperazine but not W-7 increased basal Lp in rabbit cortical collecting tubules. When cortical collecting tubules were pre-treated with either trifluoperazine or W-7, the effect of AVP to increase Lp was significantly inhibited. To determine the site of this inhibition, Lp responses to exogenous cyclic adenosine 3',5'-phosphate (AMP) were studied. Both trifluoperazine and W-7 pretreatment significantly inhibited the effect of a cyclic AMP analogue to increase rabbit cortical collecting tubule Lp. These results suggest that calmodulin may be an important mediator of the hydro-osmotic response to AVP in the mammalian cortical collecting tube by acting at a site or sites distal to cyclic AMP formation.

Treatment of a fatal transplantable erythroleukemia by procedures that lower endogenous erythropoietin

The in vitro growth of primary erythroleukemia cells has been examined in the presence and absence of the hormone erythropoietin (EPO). Although these leukemic cells had previously been considered to be hormone-independent, addition of EPO was found to be essential for maximum growth in culture. Erythroid colonies that grew in the presence of EPO were leukemogenic when returned to mice. Influence of EPO on the in vivo growth of leukemic cells was indicated by our findings that administration of the hormone caused a more severe leukemia and rapid death, and transfusion of red blood cells, which lowers endogenous EPO, led to decreased spleen size and increased survival of leukemic mice. We suggest from our results that hormone-associated therapy might be efficacious in the treatment of this and, perhaps, other leukemias.

Effects of vasopressin antagonist on vasopressin binding, adenylate cyclase activation, and water flux

We studied the effect of an arginine vasopressin (AVP) analogue, (1-[beta-mercapto-beta, beta-cyclopentamethylenepropionic acid],2-O-ethyltyrosine, 4-valine)AVP(d[CH2]5Tyr[Et]VAVP), on the stimulation of adenylate cyclase by various hormones in the isolated nephron segments and 3H-AVP binding to renal papillary membranes from the rat. The net water flux across the renal cortical collecting tubules of the rabbit was also examined. We found that d(CH2)5Tyr(Et)VAVP significantly inhibited adenylate cyclase activation by AVP in cortical, medullary, and papillary collecting tubules and in the medullary thick ascending limb. In contrast, the AVP analogue did not alter the stimulation of adenylate cyclase by parathyroid hormone in the cortical thick ascending limb, by glucagon in the medullary thick ascending limb, and by calcitonin in cortical collecting tubules. In addition, d(CH2)5Tyr(Et)VAVP blocked [3H]AVP binding to renal papillary membranes. The enhanced net water transport induced by AVP in isolated, perfused rabbit cortical collecting tubules also was completely blocked by this AVP analogue. These results indicate that d(CH2)5Tyr(Et)VAVP specifically antagonizes the cellular action of AVP on the medullary thick ascending limb and on the cortical, medullary, and papillary collecting tubules. Evidence is also presented for competitive antagonism as the cellular mechanism of action.

Forskolin increases osmotic water permeability of rabbit cortical collecting tubule

Forskolin is a unique diterpene that may directly activate the catalytic subunit of adenylate cyclase. We therefore examined the effect of 50 microM forskolin on osmotic water permeability in rabbit cortical collecting tubules perfused in vitro. Forskolin increased net volume flux (Jv, from 0.30 to 1.22 nl/mm/min, P less than 0.02) in all tubules. The hydro-osmotic effect of forskolin was similar with respect to magnitude and time course to that produced by a maximal dose (250 microU/ml) of arginine vasopressin. An additive effect on Jv and Lp was not observed when maximal concentrations of forskolin and arginine vasopressin were given simultaneously. The compound d(CH2)5Tyr(Et) VAVP, which noncompetitively inhibits the vasopressin receptor, significantly reduced collecting tubular hydro-osmotic response to arginine vasopressin. In contrast, the hydro-osmotic response to forskolin was maintained in the presence of d(CH2)5 Tyr(Et)VAVP. However, the hydro-osmotic response to forskolin could be inhibited by 1.0 microM guanine 5'-(beta,gamma-imido) triphosphate (GppNHp) and by the calmodulin inhibitor N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7). These results demonstrate that forskolin exerts an hydro-osmotic effect in the mammalian nephron which occurs independent of the vasopressin receptor. Guanine nucleotide regulatory proteins may modulate the osmotic water permeability effect of forskolin. Finally, calmodulin is required for full expression of the effect of forskolin to increase osmotic water flux.

Do alcoholic Korsakoff's syndrome patients acquire affective reactions?

In this study we report two experiments that investigate the acquisition of affective reactions. In Experiment 1, unfamiliar melodies were played to Korsakoff's syndrome patients and alcoholic and nonalcoholic control subjects who were matched with them according to age and education. Following a retention interval of 5 min, subjects received a preference test on old and new melodies. Korsakoff's syndrome patients showed the same increase in preference for old melodies as a consequence of prior exposures as control subjects did, but their recognition of melodies was significantly impaired in comparison with controls. In Experiment 2, the same subjects saw photographs of two men. Fictional biographical information depicted one as a "good guy" and the other as a "bad guy." After a retention interval of approximately 20 days, Korsakoffs recalled virtually none of the biographical information; however, 78% preferred the good guy, and impression ratings were less favorable for the bad guy. Korsakoff patients developed preferences and impressions even though they did not have voluntary access to the information on which the preferences were based. However, their impression ratings were less extreme than those of controls. The pattern of results of the two studies is discussed in terms of Johnson's (1983) MEM model of memory.

Do alcoholic Korsakoff's syndrome patients acquire affective reactions?

In this study we report two experiments that investigate the acquisition of affective reactions. In Experiment 1, unfamiliar melodies were played to Korsakoff's syndrome patients and alcoholic and nonalcoholic control subjects who were matched with them according to age and education. Following a retention interval of 5 min, subjects received a preference test on old and new melodies. Korsakoff's syndrome patients showed the same increase in preference for old melodies as a consequence of prior exposures as control subjects did, but their recognition of melodies was significantly impaired in comparison with controls. In Experiment 2, the same subjects saw photographs of two men. Fictional biographical information depicted one as a "good guy" and the other as a "bad guy." After a retention interval of approximately 20 days, Korsakoffs recalled virtually none of the biographical information; however, 78% preferred the good guy, and impression ratings were less favorable for the bad guy. Korsakoff patients developed preferences and impressions even though they did not have voluntary access to the information on which the preferences were based. However, their impression ratings were less extreme than those of controls. The pattern of results of the two studies is discussed in terms of Johnson's (1983) MEM model of memory.

The cyclic AMP system in the inner medullary collecting duct of the potassium-depleted rat

The present study was undertaken to investigate the cyclic AMP system in the isolated inner medullary collecting tubule (IMCT) of hypokalemic (HK) rats. In situ incubation of IMCT with 10(-7) M arginine vasopressin (AVP) at 300 mOsm/kg H2O in control normokalemic rats increased cyclic AMP content (fmoles/mm) from 5.68 +/- 1.41 to 30.3 +/- 5.31 (P less than 0.001). In HK rats the increase in cyclic AMP was blunted from 7.18 +/- 2.0 to 14.78 +/- 3.14 fmoles/mm (P less than 0.05 compared to controls). No such blunting was observed in the outer medullary collecting duct of hypokalemic rats, but was seen in the IMCT when studied at 800 (P less than 0.05), 1200 (P less than 0.01), and 2000 mOsm/kg H2O (P less than 0.05). The increase in cyclic AMP was also blunted in IMCT of HK rats not allowed to become polyuric or polydipsic by pair-watering studied at 300, 800, and 1200 mOsm/kg H2O. To define the process responsible for the failure to normally increase cyclic AMP in HK, adenylate cyclase activity (AC) was determined at 800 mOsm/kg H2O. While basal AC was not different, the response to all concentrations of AVP between 10(-10) and 10(-6) M was markedly depressed in tubules from HK rats. In contrast AC response to 10(-2) M NaF was not different in IMCT of normokalemic and HK rats. While the abnormal cyclic AMP content with AVP could be explained by abnormal generation, a contribution of increased metabolism was also sought.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanisms of escape from desmopressin in the rat

The mechanism(s) of renal escape from the hydro-osmotic effect of vasopressin is unknown. We therefore studied escape in conscious, unrestrained rats receiving continuous intravascular infusions of 1-deamino-8-arginine-vasopressin (desmopressin) and hypotonic fluid over 5 days. Escape from desmopressin started 8 hours after exposure and was characterized by a progressive increase in urine flow and decreases in urine osmolality and free water reabsorption. When positive water balance was prevented by matching the rate of infusion of hypotonic fluid to urine flow while maintaining the dose of desmopressin constant, escape did not occur. This suggested that water retention, rather than chronic exposure to desmopressin, mediated the escape. To elucidate the mechanism whereby water retention induces escape from desmopressin, urinary prostaglandin E2 excretion was measured and found to be increased concomitant with the onset of escape. Prevention of this increase in urinary prostaglandin E2 excretion with indomethacin resulted in additional water retention and a delay in the onset of escape. During the maintenance of escape, after significant water retention occurred, increases in mean arterial pressure, renal blood flow, and glomerular filtration rate were observed. Renal interstitial solute concentration remained constant through escape. Basal and vasopressin-stimulated collecting tubular and thick ascending limb adenylate cyclase did not differ when control and escape animals were compared. These results suggest that enhanced renal synthesis of prostaglandin E2 facilitates the early phase of escape; later, water retention results in plasma volume expansion with increases in cardiac index, arterial pressure, renal blood flow, and glomerular filtration rate. These systemic and renal hemodynamic alterations may be important in maintaining escape from desmopressin.

Further in vivo evidence for antagonist-to-antidiuretic action of arginine vasopressin

The effect of a new arginine vasopressin (AVP) analogue, [1-(beta-mercapto-beta,beta-cyclopentamethylenepropionic acid), 2-O-ethyltyrosine, 4-valine]AVP or d(CH2)5Tyr(Et)VAVP, was examined on exogenous and endogenous AVP in the conscious rat. An intravenous injection of 8 micrograms/kg body wt of the AVP analogue completely blocked the antidiuretic effect of exogenous AVP (4 ng/kg body wt iv). Similarly, 8 micrograms/kg of the AVP analogue totally abolished the antidiuretic effect of infused AVP (0.1 mU X kg-1 X min-1) in the homozygous Brattleboro rats with central diabetes insipidus. The antagonism of this antidiuretic effect of exogenous AVP occurred in the absence of changes in urinary solute excretion, glomerular filtration rate (GFR), and mean arterial pressure. Intraperitoneal administration of the AVP analogue (30 micrograms/kg body wt) decreased the mean urinary osmolality in rats after 24 h of fluid deprivation from 3,098 +/- 140 to 797 +/- 155 mosmol/kg H2O (P less than 0.001). The duration of the antagonism of endogenous AVP was approximately 4.5 h. The antagonism of AVP was not dependent on the vascular properties of AVP, since the AVP analogue also blocked the antidiuretic effect of exogenous 1-deamino-8-D-AVP (DDAVP), an AVP analogue with negligible vascular properties. These in vivo results therefore indicate that d(CH2)5Tyr(Et)VAVP is a specific antagonist of the hydrosmotic effect of exogenous and endogenous AVP. In contrast to some previous analogues, this effect of the AVP analogue occurred in the absence of any known diuretic factors including an increase in GFR, solute excretion, and blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Nutritive quality of leaf proteins coagulated at different pH

Leaf proteins obtained by coagulation at different pH were examined for their chemical composition and nutritional quality. Green juice was extracted from alfalfa, red clover, Italian ryegrass and oats and leaf protein was coagulated by heating the juice after adjusting the pH to 4 or 8-8.5, or without any adjustment of the pH (about pH 6). The mild alkaline juice from Italian ryegrass and oats did not cause the satisfactory coagulation but it was achieved with the addition of Ca salt to the juice before heating. There were no important differences in the amino acid compositions of the leaf proteins coagulated at different pH. Crude ash, Ca and Mg contents increased with an increase in pH of coagulation and the protein coagulated at pH 8 had remarkably high contents of crude ash, Ca, Mg, Na and P in each crop. The leaf protein coagulated at pH 6, on the contrary, had a high content of true protein and low contents of nitrogen free extracts and nucleic acid as compared with those at pH 4 and 8. The pH of coagulation of leaf protein from alfalfa and red clover had no effect on the nutritional quality of the respective proteins. In Italian ryegrass and oats, however, the leaf protein coagulated at pH 8 was found to be nutritionally inferior to those coagulated at a lower pH. The data presented in this work support that in general, the leaf protein produced by heating the green juice without any adjustment of pH may be suitable for protein resources because of its desirable properties, i.e. high true protein content and good nutritional quality.

Sulphide as an inhibitor and electron donor for the cytochrome c oxidase system

Anomalies both kinetic and equilibrium in nature are described for the inhibition of cytochrome c oxidase activity by sulphide in the isolated enzyme and in submitochondrial particles. These anomalies are related to the involvement of more than 1 mol of sulphide in the blockage of one cytochrome aa3 centre. Sulphide reduces resting cytochrome a3, a reaction that results in oxygen uptake and the loss of a sulphide molecule. Sulphide can also reduce cytochromes c and a; in the former case, a part of the one-equivalent oxidation product, presumed to be the SH radical, reacts with oxygen. Such oxygen uptake is also seen under aerobic conditions when ferricyanide reacts with sulphide. Three phases are identified in the inhibitory interaction of sulphide with the cytochrome c oxidase enzyme itself: an initial rapid reaction involving sulphide oxidation, oxygen uptake, and conversion of cytochrome aa3 into the low-spin "oxyferri" form; a subsequent step in which sulphide reduces cytochrome a; and the final inhibitory step in which a third molecule of sulphide binds the a3 iron centre in the cytochrome a2+ a3 3+ (oxy) species to give cytochrome a2+ a3 3+ H2S. the initial events parallel some of the events in the interaction of the cytochrome c-cytochrome aa3 system with monothiols; the final inhibitory event resembles that with cyanide.

Use of Denver shunt in recurrent hepatic hydrothorax

A 49-year-old woman with alcoholic cirrhosis was hospitalized for severe respiratory distress. A moderate amount of ascites was noted on physical examination, and the right hemithorax was completely opacified on the chest x-ray film. Thoracentesis was performed, and a follow-up chest x-ray film showed marked reduction of pleural effusion. Two days later the patient again was in respiratory distress, and a chest tube was inserted. On the tenth hospital day, a peritoneovenous (Denver) shunt was inserted and the chest tube was removed. Follow-up chest x-ray films showed almost complete resolution of pleural effusion, and the patient has remained free of symptoms. When hepatic hydrothorax does not respond to conventional therapy, we believe aggressive treatment with a Denver shunt may be successful. To our knowledge this procedure has been performed successfully in only one other patient. Further study is needed to assess its value as a possible alternative method of treatment.

Effect of potassium depletion on the vasopressin-sensitive cyclic AMP system in rat outer medullary tubules

The effects of PDN on VP-sensitive cAMP metabolism were examined in MCT and MAL microdissected from the rat kidney. VP-sensitive adenylate cyclase activity was significantly reduced (delta -46%; p less than 0.05) in MAL of PDN rats but, in sharp contrast, was significantly increased (delta +79%; p less than 0.02) in MCT of PDN rats compared to controls. cAMP phosphodiesterase activity was significantly increased in both MAL (delta +59%; p less than 0.005) and MCT (delta +79%; p less than 0.001) of PDN rats compared to controls. The increase in cAMP accumulation in MAL measured in response to VP in intact tubules did not differ between PDN and controls, whereas cAMP accumulation in response to VP was significantly higher (delta +127%; p less than 0.001) in MCT of PDN rats compared to controls. The present results would indicate that the observed in vivo resistance to the antidiuretic effect of VP that occurs in PDN is not due to an impairment in VP-sensitive cAMP accumulation in MCT, but would rather suggest that a defect exists at a cellular step subsequent to cAMP generation. In addition, our results illustrate that the extent and directionality of in situ accumulation of cAMP measured in intact tubules cannot always be predicted from rhe activities of enzymes controlling its synthesis and degradation (adenylate cyclase and cAMP phosphodiesterase), which are measured in vitro in disrupted tubules.

Oxidation of sulphide by cytochrome aa3

The effectiveness of H2S as an inhibitor of cytochrome c oxidase increase (Ki decreases) with sulphide concentration. A spectroscopic change in cytochrome aa3 is induced aerobically by sulphide at the same rate as that calculated for inhibition. The initial spectroscopic product is not inhibited, but an 'oxygenated' (oxyferri) form of the enzyme. Stoichiometric sulphide addition to cytochrome aa3 under anaerobic conditions produces another low-spin form of the enzyme; subsequent admission of oxygen gives rise to the 607 nm compound. At high enzyme levels sulphide itself acts as a substrate measured polarographically, with an oxygen uptake proportional to the amount of sulphide added. Binding of sulphide to ferric enzyme probably causes reduction at the oxygen-sensitive a3-Cu centre, which is followed aerobically by reoxidation to the oxyferri state via the 607 nm intermediate. A stable sulphide complex is formed only after the reduction of cytochrome a; but once formed this inhibited species is retained if cytochrome a is reoxidized.

Membrane immunoglobulins of spontaneous B lymphomas of aged BALB/c mice

Four cell lines derived from spontaneous BALB/c lymphoma tumors were analyzed with regard to the type of their membrane immunoglobulins (Ig). Using lactoperoxidase iodination of membrane proteins combined with immunoprecipitation and electrophoresis on polyacrylamide gel, three of these cell lines (X16c, L10A and K46) were found to express the monomeric form of IgM and IgD as well as half molecules. One cell line (M12) lacked both IgM and IgD. The apparent mol. wt of the lymphoma micro chain was about 80 000 and exceeded the mol. wt. of 75 000 determined for micro chains secreted by myeloma cells. The mol. wt. of the delta heavy chain was found to be 66 000. Immunofluorescence showed that the L10A and X16c lines expressed lambda light chains on their cell surface. Another Ig-bearing cell line (K46) expressed both lambda and kappa chains. Thus, three out of the four B lymphomas examined expressed both IgM and IgD with light chains of the Lambda type. These results, together with our previous findings which demonstrate the presence of Ia and Fc receptors on the same cells, indicate that spontaneous B lymphomas in BALB/c mice are the malignant counterpart of mature B lymphocytes.

Alkaline phosphatase in adaptation to low dietary phosphate intake

Previous findings suggest that alkaline phosphatase (Alk Pase) may be involved in phosphate transport. Since phosphate reabsorption is enhanced in the kidney and duodenum of animals stabilized on a low-phosphorus diet (LPD), Alk Pase was measured in the kidney, small intestine, and other tissues in LPD rats. In particulate fractions from the renal cortex, intestine, renal medulla, liver, and heart ventricle from LPD rats the activity of Alk Pase was significantly increased but the activities of other plasma membrane enzymes were not different between control and LPD groups. The increased Alk Pase in the renal cortex was localized to the brush border of the proximal tubule histochemically and by measurement of Alk Pase in brush-border preparations. Also in the renal cortex, typical enzymes associated with mitochondria, lysosomes, and cytosol were unchanged with the exception of cytosolic adenosine 3',5' cyclic-monophosphate phosphodiesterase, which was increased in LPD rats. Alk Pase in the renal cortex and intestine may play a role in the enhanced phosphate reabsorption in LPD animals.

Insulin inhibition of hormone-stimulated protein kinase systems of rat renal cortex

Parathyroid hormone (PTH) and glucagon increase the urinary fractional excretion of phosphate, but insulin administration is associated with a decreased fractional excretion of phosphate. It was the purpose of this study to determine whether insulin will antagonize the effects of PTH and glucagon on cAMP levels and protein kinase activation of rat renal cortex. In situ incubation studies were performed on rat renal cortical slices exposed to insulin, PTH, and glucagon. Insulin alone did not affect the tissue cAMP and cGMP levels or the state of protein kinase activation. Preincubation of slices with insulin, however, did significantly inhibit increases in protein kinase activation induced by both PTH and glucagon. Insulin also significantly inhibited PTH-stimulated increases in tissue cAMP levels, but did not blunt the elevations of cAMP levels induced by glucagon. Insulin (10(-9) M) had no effect on either the in vitro activity of adenylate cyclase, basal or PTH-stimulated, or on the activities of low Km cytosolic or membrane-bound cAMP phosphodiesterase. The data show that insulin antagonizes activation of protein kinase by both PTH and glucagon in renal cortex. Separate mechanisms are probably involved for PTH and glucagon interaction. The antiphosphaturic effect of insulin in vivo may result in part from this antagonism at the cellular level.

Effect of hippocampus extirpation in the rat on glutamate levels in target structures of hippocampal efferents

Twenty days after complete uni- or bilateral hippocampus extirpation in rats, a 25% decrease in glutamate concentration was observed in the septum. Glutamate content also decreased in other terminal structures of the hippocampo-subicular system, i.e. entorhinal cortex, nucleus accumbens septi, mammillary bodies and contralateral hippocampus. It is concluded that the fall in glutamate content which is absent in caudate nucleus is specific for target regions of the hippocampal efferents, adding further support to the suggested transmitter role of glutamate in the limbic system.