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Biomedical subjects

P Needleman

Publications and source records attributed to P Needleman.

At least 127 records · Page 7Linked to original sources
PubMed1985

Atriopeptins: renal-specific vasodilators in conscious dogs.

Conscious dogs were instrumented to study the effects of atriopeptins (I, II, III) on renal, iliac, mesenteric, and coronary blood flow. Intravenous injection of atriopeptins II and III caused a dose-related increase in renal blood flow, whereas atriopeptin I had no effect. Atriopeptins II and III at 5 micrograms/kg increased renal blood flow 27 +/- 5.0% from 252 +/- 29 ml/min and 18 +/- 2.9% from 238 +/- 32 ml/min and reduced renal vascular resistance 24 +/- 3.2% from 0.431 +/- 0.048 mmHg X ml-1 X min and 15.1 +/- 1.2% from 0.443 +/- 0.023 mmHg X ml-1 X min, respectively. Atriopeptin I, II, or III exerted no significant effect on systemic arterial pressure, heart rate, coronary, mesenteric, or iliac blood flows. Doses of nitroglycerin (25 micrograms/kg) that increased renal blood flow (28 +/- 5.0%) to a degree comparable to atriopeptins II and III also caused increases in coronary, iliac, and mesenteric blood flows and produced falls in systemic blood pressure and a reflex tachycardia. Thus in the conscious dog, atriopeptins II and III are potent selective renal vasodilators that do not exhibit systemic hemodynamic effects in contrast to nitroglycerin, a nonselective vasodilator. Cleavage at the carboxy terminal end of these peptides to yield atriopeptin I abolishes the renal vasodilator action entirely.

Anesthesia↗
PubMed1985

Atriopeptins: correlation between renal vasodilation and natriuresis.

The effect of atrial peptides on renal function was studied in intact anesthetized dogs. A quantitative comparison of bolus intra-arterial injections demonstrated a rank order potency as renal vasodilators and natriuretic/diuretic agents as follows: ser-leu-arg-arg-atriopeptiin III (SLRR-APIII) greater than high molecular weight artrial peptide greater than or equal to atriopeptin (AP)III = APII much greater than API (essentially inactive). A sustained infusion of APIII was employed in order to study the temporal and quantitative correlation of the renal functional changes induced by the atrial peptide. Both intra-arterial and intravenous administration of the peptide produced concentration-dependent increases in renal blood flow, urine volume, sodium excretion, and osmotic clearance. Infusion of APIII into the renal artery did not alter systemic blood pressure or heart rate. Intravenous infusions of APIII required 10 times higher doses to induce the changes in renal vascular resistance and electrolyte excretion, and a fall in blood pressure and tachycardia resulted. The natriuretic-diuretic effect of the atriopeptins appears to be closely associated with renal vasodilation, exhibiting a positive linear correlation between the peptide-induced changes in sodium excretion and changes in renal blood flow.

Animals↗
PubMed1985

Comparative vascular pharmacology of the atriopeptins.

The atriopeptins are potent relaxants of norepinephrine-constricted aortic strips or are dilators of renal blood vessels in isolated perfused rat kidneys that are constricted by norepinephrine. This vasorelaxant property of the atriopeptins requires the presence of phenylalanine arginine (i.e., atriopeptin II, III, or ser-leu-arg-arg atriopeptin III) residues in the carboxy terminus which are considerably more effective than atriopeptin I (the 21 amino acid peptide which lacks the phe-arg C-terminus) or the core peptide (residues 3-19). However, these artificially in vitro precontracted preparations do not accurately predict the vascular effectiveness of the atriopeptins in intact rats. Intravenous administration of the atriopeptins (including atriopeptin I) to anesthetized rats produces concentration-dependent hypotension, a selective decrease in renal resistance in low doses (determined with microspheres), and pronounced diuresis. At higher doses, atriopeptins increase blood flow in other vascular beds. On the other hand, in the anesthetized dog, injection (intraarterially) of the phe-arg-containing peptides produces a concentration-dependent increase in both renal blood flow and sodium excretion, whereas atriopeptin I is inactive. Although there is a species difference in responsiveness to atriopeptin I, these data demonstrate a direct correlation between the renal vasodilation and diuresis produced by this novel family of atrial peptides.

Animals↗
PubMed1985

Inhibition of aldosterone biosynthesis by atriopeptins in rat adrenal cells.

The effect of synthetic atriopeptins on basal and stimulated aldosterone secretion was determined in isolated adrenal glomerulosa cells of the rat. Neither atriopeptin I (1-21) or III (1-24, i.e., the Phe-Arg-Tyr carboxy-terminal extension of atriopeptin I) altered basal aldosterone release. However, if the cells were prepared from adrenals of sodium-depleted rats, the basal aldosterone release was increased by 9-fold, compared with cells from normal rats. This elevated release was inhibited by 32% by atriopeptin I and atriopeptin III. Atriopeptin III was more potent than atriopeptin I. Angiotensin II and adrenocorticotropin stimulated the release of aldosterone in a concentration-related manner. Both atriopeptin I and atriopeptin III inhibited the stimulation by the peptides. Atriopeptin I inhibited angiotensin II- and adrenocorticotropin-induced aldosterone production by 50% at concentrations of 12 and 11 nM, respectively, and 0.5 and 0.2 nM, respectively, for atriopeptin III. Potassium-stimulated aldosterone production was also inhibited by atriopeptin I and atriopeptin III with 50% inhibition at concentrations of 10 and 0.4 nM, respectively. Shorter peptides (1-20, 1-19, and 3-19) were equipotent to atriopeptin I (1-21) as inhibitors of angiotensin II-induced steroidogenesis. To determine the site at which atriopeptins inhibit aldosterone synthesis, we used cyanoketone to inhibit 3 beta-hydroxy-dehydrogenase and dissociate the early and late pathways. Angiotensin II (2 nM) increased the synthesis of pregnenolone (early pathway), as well as the conversion of [3H]corticosterone to [3H]aldosterone (late pathway). Atriopeptin III inhibited basal pregnenolone synthesis by 36% and completely blocked angiotensin II-stimulated synthesis. The peptide similarly inhibited the late pathway.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Glands↗
PubMed1985

Effects of endogenously produced leukotrienes, thromboxane, and prostaglandins on coronary vascular resistance in rabbit myocardial infarction.

In an effort to evaluate the synthesis and function of eicosanoids in myocardial infarction, we have developed a technique of in vivo myocardial infarction in rabbits followed by ex vivo cardiac perfusion. Isolated Langendorff perfused infarcted hearts (removed 1 or 4 d after infarction) responded to the inflammatory cell agonist N-formylmethionyl-leucyl-phenylalanine (fMLP) with (a) the release of leukotrienes B4, C4, and D4; (b) the release of large amounts of thromboxane (235 +/- 66 ng/5 min), prostacyclin (714 +/- 285 ng/5 min), and prostaglandin E2 (PGE2) (330 +/- 108 ng/5 min); and (c) a coronary vasoconstriction (21.1 +/- 2.5% increase in coronary perfusion pressure) that was specifically inhibited by the peptidoleukotriene receptor antagonist FPL-55712. While noninfarcted hearts challenged with fMLP also released leukotrienes B4, C4, and D4, they released only small amounts of the cyclooxygenase products (thromboxane, 30 +/- 9 ng/5 min; prostacyclin, 120 +/- 54 ng/5 min; PGE2, 27 +/- 10 ng/5 min) and showed minimal vasoconstriction (5.6 +/- 2.1% increase in perfusion pressure). Similarly, hearts challenged with fMLP 30 d following infarction released only small amounts of the cyclooxygenase products (thromboxane, 42 +/- 8 ng/5 min; prostacyclin, 386 +/- 31 ng/5 min; PGE2, 79 +/- 25 ng/5 min). When bradykinin was administered, no leukotrienes were produced, but acutely infarcted hearts released 10 times more thromboxane, prostacyclin, and PGE2 than normal hearts and significantly larger amounts of these products than 30-d infarcted hearts. Histologic analysis showed no inflammatory cells in normal hearts, a prominent polymorphonuclear leukocyte infiltration in 1-d infarcted tissue, fibroblast proliferation with mononuclear cell invasion in 4-d infarcted tissue, and a fibrotic scar with scanty mononuclear cell infiltrate in 30-d infarcted tissue. Inflammatory cell invasion was temporarily associated with augmented cyclooxygenase metabolism, suggesting that infiltrating leukocytes may be responsible for production of thromboxane, prostacyclin, and PGE2 in acutely infarcted hearts. The finding that endogenously produced peptidoleukotrienes are potent coronary vasoconstrictors in infarcted rabbit hearts suggests that these products may contribute to tissue injury in myocardial infarction.

Animals↗
PubMed1985

Thromboxane synthase is preferentially conserved in activated mouse peritoneal macrophages.

Resident macrophages isolated from uninfected animals produce large quantities of arachidonic acid (AA) metabolites. Immunizing animals with protein antigens or bacteria activates macrophages and causes an 80% reduction in the cyclooxygenase and lipoxygenase metabolites relative to resident cells. Since some products have been shown to modulate immune functions, we examined how the AA metabolic enzyme activities regulate the products that are synthesized. We demonstrate that the cyclooxygenase, 5-lipoxygenase, prostacyclin synthase, and probably prostaglandin (PG) endoperoxide E-isomerase activities were decreased in activated peritoneal macrophages. In sharp contrast, thromboxane synthase activity was selectively unchanged or enhanced in the activated macrophages. Thus the immune response appears to modulate the activity of the AA and PG endoperoxide-dependent enzymes, thus dictating a major shift in the profile of metabolites synthesized by macrophages.

Animals↗
PubMed1985

Atriopeptin III. A potent natriuretic, diuretic, and hypotensive agent in rats with chronic renal failure.

Chronic renal failure is frequently associated with volume overload, resulting in hypertension and, in some cases, congestive heart failure. Atriopeptin III (AP III), a 24-amino acid atrial peptide, is a potent vasodilator and natriuretic/diuretic agent in normal rats. An infusion of AP III at 0.2 microgram/kg per min for 60 min produced dramatic responses in animals with chronic renal failure (5/6 nephrectomy 4 wk before study). Systemic blood pressure fell 20% by the end of infusion. A pronounced rise in glomerular filtration rate (24%) was maintained during the infusion period when urine flow rate was stable (35-60 min), even though renal blood flow was unchanged from base line. Urinary volume increased 4.4-fold and sodium excretion increased 9 to 12-fold during the infusion. Fractional excretion of sodium ranged between 9 and 15% in those animals whose initial GFR values were lower than 0.5 ml/min. We conclude that AP III is a potent natriuretic/diuretic agent in rats with reduced renal mass, presumably exerting that effect predominantly through increases in GFR. This agent may well be useful in the treatment of volume overload in patients with chronic renal failure.

Animals↗
PubMed1985

Vasodilator properties of a family of bioactive atrial peptides in isolated perfused rat kidneys.

The isolated Krebs-perfused rat kidney was used for the quantitative and qualitative evaluation of the family of peptides derived from rat atrial extracts. Renal resistance changes were measured in perfused rat kidneys continuously infused with norepinephrine. The low molecular weight peptide fraction from rat atrial extracts was purified to obtain six peptides. The 21 amino acid peptide, designated atriopeptin I, was previously demonstrated to be natriuretic and to relax intestinal but not vascular smooth muscle strips (in vitro) and to be an extremely weak renal spasmolytic in the isolated perfused rat kidney. On the other hand, the 23 amino acid peptide (which has a Phe-Arg carboxy-terminal extension on atriopeptin I), designated atriopeptin II, and atriopeptin III (the Phe-Arg-Tyr carboxy-terminal extension) were natriuretic and spasmolytic (in vitro) on both intestinal and vascular smooth muscle. Both atriopeptin II and III produced a profound concentration-dependent decrease in renal resistance in the norepinephrine-constricted rat kidney preparation. A comparative study of the six peptides isolated from atrial extracts indicates that the Phe-Arg or Phe-Arg-Tyr carboxy-terminal extension of the basic 21 amino acid sequence is essential for the renal vasorelaxant activity. A purified high molecular weight peptide (designated atriopeptigen) is impotent relative to the low molecular weight atriopeptin II and III as a renal spasmolytic in isolated perfused rat kidneys and reduces renal resistance only after in vitro proteolytic cleavage. Thus, the low molecular weight peptides atriopeptin II and III appear to be the active species that mediate the renal vasodilation produced by atrial extracts.

Animals↗
PubMed1985

Arachidonate metabolism in renal injury.

In conclusion, the evidence to date demonstrates that the enhanced arachidonate metabolism seen in hydronephrosis is responsible for the pathophysiological alterations observed in this model of renal injury. The balance between vasodilating prostaglandins and the vasoconstrictor thromboxane A2 may be critical in determining blood flow to the obstructed kidney. The alterations in arachidonate metabolism in this pathophysiologic state appear to result from the invasion of macrophages and the proliferation of fibroblasts in the cortical interstitium. Additionally, the macrophage appears to be necessary for the expression of the enhanced hormone-stimulated arachidonate metabolism. We envision the temporal sequence of events in this model to be as follows: ureter obstruction causes a mechanical disruption and/or immunologic stimulus in the cortex, which triggers a regional inflammatory response resulting in the proliferation of interstitial cells and the invasion of mononuclear cells. The macrophages, which are in direct contact with fibroblasts, are capable of releasing a factor that stimulates fibroblast proliferation, cortical microsomal cyclooxygenase activity, and prostaglandin E2 release (i.e., intrinsic arachidonate metabolism). The enhanced thromboxane synthetase levels and thromboxane A2 appear to come from the macrophage. The prostaglandin E2 and thromboxane A2 released modulate vascular tone. Prostaglandin E2 may also serve as an inhibitor of macrophage function. Two other models of renal damage also exhibit marked enhancement of renal prostaglandin synthesis and induction of thromboxane production: renal venous occlusion (32) and glycerol-induced acute renal failure (3). The finding that several models of renal damage have definite quantitative and qualitative alterations in the prostaglandin cascade reflects the importance of this pathway in renal pathophysiology.

Angiotensin II↗
PubMed1985

Exaggerated human vascular cell prostaglandin biosynthesis mediated by monocytes: role of monokines and interleukin 1.

Incubation of cultured human umbilical vein endothelial cells with factors derived from human peripheral blood mononuclear cells (MNCF) or adherent monocytes (AMF) resulted in concentration-and time-dependent increases in prostacyclin and prostaglandin E2 (PGE2) production. MNCF and AMF also stimulated prostacyclin and PGE2 biosynthesis in cultured human arterial smooth muscle cells and human dermal fibroblasts. The effect of these monokines on endothelial cells and fibroblasts was mimicked by treatment with purified human interleukin 1 (IL 1). Mononuclear cell-conditioned medium subjected to gel filtration yielded fractions (Mr 12,000 to 18,000 daltons) which simultaneously contained endothelial cell and fibroblast prostaglandin-stimulating activity and IL 1 activity. Therefore, monokines, specifically IL 1, appear to serve as chemical mediators of the interaction between monocytes and vascular cells as would occur in blood vessel injury, inflammation, and atherosclerosis.

6-Ketoprostaglandin F1 alpha↗
PubMed1984

Atriopeptin release from the isolated perfused rabbit heart.

Mammalian atrial extracts have been shown to contain bioactive peptides which exert natruiretic, diuretic, and smooth muscle relaxant effects. These extracts include several low molecular weight (less than 5,000 Mr) atrial peptides (atriopeptins) which exhibit identical sequences over a central core region which are derived from the high molecular weight peptide (atriopeptigen) precursor which has been purified and sequenced. In the current study we found that extracts of rabbit atria possess both high and low molecular weight bioactive atrial peptides, however, the coronary venous effluent obtained from the isolated perfused rabbit heart only contained the low molecular weight peptide. This trypsin labile activity causes a dose-dependent relaxation of rabbit aorta and chicken rectum assay strips. Separation of the bioactivity with gel filtration chromatography and reversed phase HPLC indicates the heart releases a single substance similar to atriopeptin III. There was no evidence that atriopeptigen was released from the isolated perfused rabbit heart. We suggest that atriopeptigen is proteolytically processed in the atria to an atriopeptin which is subsequently the released form of the atrial peptide.

Animals↗
PubMed1984

A novel cyclooxygenase metabolite of arachidonic acid.

The 8000 X g pellet of rabbit placenta transformed arachidonic acid into a number of lipoxygenase and cyclooxygenase products of known structure. A metabolite was also produced which was inhibited by indomethacin and required calcium for its formation. This compound had a UV absorption maximum at 227 nm under acidic or neutral conditions and gave a bathochromic shift to 281 nm under alkaline conditions. Reduction of this metabolite with sodium borohydride produced prostaglandin (PG) F2 alpha (as determined by mass spectrometry), while catalytic hydrogenation increased the molecular weight by four mass units, indicating the presence of two double bonds. Based on the mass spectrum of the derivatized metabolite, the structure proved to be 9,15-dioxo-11-hydroxyprosta-5,13-dienoic acid. This compound is produced by the term placenta and does not appear to be formed from PGE2, PGF2 alpha, or PGD2. The compound is suppressed by GSH and NADPH, but its formation is not increased by NAD or NADP. PGH2 and PGG2 are not converted to 9,15-dioxo-11-hydroxyprosta-5,13-dienoic acid under similar in vitro incubation conditions. This therefore represents conversion of arachidonate to 9,15-dioxo-11-hydroxyprosta-5,13-dienoic acid through a Ca2+-dependent, non-PG dehydrogenase pathway.

Animals↗
PubMed1984

Arachidonic acid metabolic pathways in the rabbit pericardium.

Minced rabbit pericardium actively converts [1-14C]arachidonic acid into the known prostaglandins (6-[1-14C]ketoprostaglandin F1 alpha, [1-14C]prostaglandin E2 and [1-14C]prostaglandin F2 alpha) and into several unidentified metabolites. The major metabolite was separated by C18 reverse-phase high-pressure liquid chromatography (HPLC) and identified by gas chromatography-mass spectrometry (GC-MS) to be 6,15-[1-14C]diketo-13,14-dihydroprostaglandin F1 alpha. The other nonpolar metabolites were 15-[1-14C]hydroxy-5,8,11,13-eicosa-tetraenoic acid (15-HETE), 11-[1-14C]hydroxy-5,8,12,14-eicosatetraenoic acid (11-HETE) and 12-[1-14C]hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE). Arachidonic acid metabolites actively produced by the pericardium could influence the tone of surface blood vessels on the myocardium.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1984

The sequence of an atriopeptigen: a precursor of the bioactive atrial peptides.

The high molecular weight fraction ( atriopeptigen -APG) obtained by gel filtration chromatography of rat atrial extracts was fractionated by isoelectric focusing and reverse phase HPLC to obtain a pure APG. Purification of cyanogen bromide digests of the crude high molecular weight fraction resulted in the isolation of a single biologically active cyanogen bromide cleavage peptide. Sequence analyses of these peptides coupled with recent reports of sequence analyses of intermediate molecular weight atrial peptides ( Thibault , et al. (1984) FEBS Letters 167, 352-356, and Kangwa , et al., Biochem. Biophys. Res. Commun 119, 933-940) provide the complete primary structure of an 111 residue APG.

Amino Acid Sequence↗
PubMed1984

In vivo inhibition of thromboxane synthetase in infarcted canine myocardium.

The in vivo effectiveness of the thromboxane synthetase inhibitor OKY-1581 was tested in normal and infarcted canine myocardium. A rapid in vitro assay was developed which permits an accurate assessment of the status of the tissue thromboxane synthetase at the time of sacrifice. Reperfused infarcts were created by two hours of coronary artery occlusion followed by release of occlusion and three days of recovery. OKY-1581 was infused at 100 micrograms/kg/min for 15 minutes, a dose previously found to cause an 85% inhibition of canine platelet thromboxane synthetase in vivo. The heart was rapidly excised and transmural tissue plugs of infarcted and normal areas were obtained. These were incubated for 5 minutes with prostaglandin endoperoxide (PGH2) in phosphate buffer. Thromboxane production was inhibited from 16 +/- 1 ng TxB2 per tissue plug to 5 +/- 1 in normal myocardium and from 27 +/- 5 to 6 +/- 1 in infarcted areas of myocardium. Control incubations showed no further inhibition with the in vitro addition of 20 micrograms/ml OKY-1581, confirming the completeness of in vivo inhibition. Thus significant inhibition of thromboxane synthetase by intravenous OKY-1581 occurs even in a reperfused zone of infarction.

Acrylates↗