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Biomedical subjects

B L Roth

Publications and source records attributed to B L Roth.

At least 91 records · Page 5Linked to original sources
PubMed1987

Elevation of arterial pressure in rats by two new vertebrate peptides FLFQPQRF-NH2 and AGEGLSSPFWSLAAPQRF-NH2 which are immunoreactive to FMRF-NH2 antiserum.

We found that two recently characterized neuropeptides Phe-Leu-Phe-Gln-Pro-Gln-Arg-Phe-NH2 (F-8-F-NH2) and Ala-Gly-Glu-Gly-Leu-Ser-Ser-Pro-Phe-Trp-Ser-Leu-Ala-Ala-Pro-Gln-Arg-Phe-NH2 (A-18-F-NH2) elevate mean arterial blood pressure (MAP) in conscious, unrestrained rats. The pressor activities of both agents were attenuated, but not abolished, by prior treatment with guanethidine or prazosin. These results suggest that F-8-F-NH2 and A-18-F-NH2 elevate MAP in rats by potentiating the release of catecholamines and by mechanisms independent of catecholamine release.

Animals↗
PubMed1987

Characterization of two [3H]ketanserin recognition sites in rat striatum.

Two [3H]ketanserin recognition sites are present in the rat striatum. The high-affinity site (KD, 0.39 nM) is similar to the 5-hydroxytryptamine2 (5-HT2) site previously characterized by various investigators. The low-affinity site (KD, 21.8 nM) has a unique pharmacologic specificity and is preferentially localized to rat striatum and septum. Conventional 5-HT2 antagonists as well as 5-HT and 5-HT uptake inhibitors are ineffective at inhibiting [3H]-ketanserin binding to this low-affinity site. Also, chronic treatment with p-chlorophenylalanine, which depletes brain 5-HT, upregulates only the high-affinity site. Thus, in the striatum and septum, [3H]ketanserin labels a unique recognition site. This site has recently been shown to be associated with dopaminergic nerve endings and may regulate biogenic amine release.

Animals↗
PubMed1987

Altered hepatic vasopressin and alpha 1-adrenergic receptors after chronic endotoxin infusion.

Sepsis and septic shock are complicated by a number of hemodynamic and metabolic aberrations. These include catecholamine refractoriness and altered glucose metabolism. Recently, a nonshock rat model of continuous endotoxin infusion via an implanted osmotic pump was developed that reproduces some of the metabolic and cardiovascular findings of human sepsis. By using this model, we have found a decreased number of hepatic plasma membrane alpha 1-adrenergic and [Arg8]vasopressin receptors in rats continuously infused with endotoxin. There was a significant decrease in [3H]prazosin (35 +/- 7%) and [3H] [Arg8]vasopressin (43 +/- 8%) receptors after 30 h of continuous endotoxin infusion with no change in affinity. The ability of norepinephrine to form the high-affinity complex with alpha 1-adrenergic receptors was not altered after chronic endotoxin infusion. The results are consistent with the concept that alterations in receptor number might underlie certain of the metabolic consequences of chronic sepsis.

Animals↗
PubMed1987

Perturbation of transmembrane signaling mechanisms in acute and chronic endotoxemia.

Our results reviewed here may be summarized as follows: 1. Continuous endotoxemia significantly interferes with Ca2+-dependent information flow in the liver. 2. The subcellular sites where these molecular lesions can be localized include: a.) the plasma membrane-there are effects at the level of alpha 1-adrenergic and vasopressin binding, and also in the coupling of receptor activation to inositol lipid metabolism in terms of PIP2 degradation and resynthesis b.) the endoplasmic reticulum in terms of Ca2+ release and PI synthesis. Another one of the sequelae of Ca2+-associated receptor activation, namely, cytosolic ionized Ca2+ concentration is also affected. 3. Finally, in addition to seeing the impact of acute or continuous endotoxemia at the level of receptor activation and signal generation, we can also document alterations in the expression of physiologic function subserved by these Ca2+- and inositol lipid-associated signaling processes--i.e. in glycogen phosphorylase activity-being consistent with the above described changes. In conclusion, we state that a causal link is shown between receptor binding, agonist-induced phosphoinositide hydrolysis, intracellular Ca2+ mobilization and activation of phosphorylase a in the liver, suggesting that these alterations may underlie some of the metabolic consequences of chronic sepsis.

Acute Disease↗
PubMed1986

BAY k 8644, a calcium channel agonist, reverses hypotension in endotoxin-shocked rats.

The hypotension and depressed myocardial function frequently observed in endotoxin-induced shock are difficult to overcome pharmacologically. In this paper we demonstrate that the calcium channel agonist BAY k 8644 potently elevates blood pressure in endotoxin-shocked rats. A one time dose as low as 10 micrograms/kg of BAY k 8644 significantly elevated mean arterial pressure (MAP) in endotoxin-treated hypotensive rats while having minimal effects in normal rats. The maximum BAY k-induced percentage increase in MAP was greater in endotoxin-treated rats when compared with saline-treated control (153% vs. 120% increase respectively). BAY k 8644 also caused a dose-dependent decrease in heart rate of 37% in endotoxin-treated rats and 39% in control rats (NS vs. control). No differences in the regulatory properties of [3H]nitrendipine binding sites were discerned comparing control and endotoxin-treated rats. Thus, the enhanced activity of BAY k 8644 in hypotensive rats was not due to augmented affinity for the cardiac dihydropyridine binding site. These results demonstrate that the use of calcium channel agonists might represent a unique pharmacologic approach in pathologic states characterized by hypotension and diminished cardiac function.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1986

Phorbol esters inhibit alpha 1-adrenergic receptor-stimulated phosphoinositide hydrolysis and contraction in rat aorta: evidence for a link between vascular contraction and phosphoinositide turnover.

We investigated the actions of two biologically active phorbol esters, phorbol dibutyrate (PDB) and phorbol myristate acetate (PMA), on receptor-stimulated phosphoinositide hydrolysis in rat aorta. We found both PDB and PMA potently inhibited norepinephrine (NE) stimulated PI hydrolysis in rat aortic rings. The biologically inactive phorbol, 4-alpha-phorbol was ineffective. In the presence of the calcium channel antagonist nitrendipine, PDB potently inhibited both the phasic and tonic components of NE-induced contraction. These results suggest a functional coupling between receptor-stimulated PI turnover and vascular contraction. They also suggest a mode of feed-back regulation in vascular tissue involving phorbol esters in receptor-stimulated PI hydrolysis.

Animals↗
PubMed1986

Coupling of inositol phospholipid metabolism with excitatory amino acid recognition sites in rat hippocampus.

Ibotenate, a rigid structural analogue of glutamate, markedly enhances the hydrolysis of membrane inositol phospholipids, as reflected by the stimulation of [3H]inositol monophosphate formation in rat hippocampal slices prelabeled with [3H]inositol and treated with Li+. Quisqualate, homocysteate, L-glutamate, and L-aspartate also induce a significant (albeit weaker) increase in [3H]inositol monophosphate formation, whereas N-methyl-D-aspartate, kainate, quinolinate, and N-acetylaspartylglutamate are inactive. The increase in [3H]inositol monophosphate formation elicited by the above-mentioned excitatory amino acids is potently and selectively antagonized by DL-2-amino-4-phosphonobutyric acid, a dicarboxylic amino acid receptor antagonist. These results suggest that, in the hippocampus, a class of dicarboxylic amino acid recognition sites is coupled with phospholipase C, the enzyme that catalyzes the hydrolysis of membrane inositol phospholipids.

Animals↗
PubMed1986

Pharmacologic manipulation of the peripheral vasculature in shock: clinical and experimental approaches.

An improved understanding of the patho-physiological and biochemical changes that occur in shock states has led to new and innovative pharmacologic approaches to shock reversal. In this article, we review the actions of several pharmaceutical agents on the peripheral vasculature in shock states. Agents with known efficacy, probable utility, and possible usefulness are each discussed. A model of factors modulating alpha-1 adrenergic receptor action is presented.

Adrenal Cortex Hormones↗
PubMed1986

Hepatic alpha 1-adrenergic receptor alteration in a rat model of chronic sepsis.

Catecholamine therapy is often ineffective in reversing the peripheral vasodilatation and hypotension of septic shock. This suggests that catecholamines might not be able to activate alpha 1-adrenergic receptors to cause vasoconstriction. Despite elevations in endogenous catecholamines, hypoglycemia is also a complication of human sepsis, suggesting that among many other causes, hepatic alpha 1-receptors might be altered. To better understand the pathophysiologic basis for this pharmacologic dilemma, we studied the effect of experimental sepsis on alpha 1-adrenergic receptors in hepatic tissue, a rich source of alpha 1-receptors, from septic and control Sprague-Dawley rats. alpha 1-adrenergic receptors were measured with [3H]-prazosin and data analyzed by a computerized nonlinear least-square regression algorithm. Twenty-four hours following cecal ligation with puncture, a decreased number of alpha 1-adrenergic receptors was noted in crude and purified plasma membrane fractions (23 and 40% reductions respectively) from septic animals. No changes in either agonist or antagonist affinity for receptors from septic animals were noted. These data indicate that the catecholamine refractoriness seen in septic shock may be a result of alterations in alpha 1-adrenergic receptor number or receptor-effector coupling.

Animals↗
PubMed1986

5-Hydroxytryptamine2 receptors coupled to phospholipase C in rat aorta: modulation of phosphoinositide turnover by phorbol ester.

In rat aorta, 5-hydroxytryptamine (5-HT) stimulated phosphoinositide (PI) turnover and contraction (EC50 = 10 +/- 3 microM); these two responses were highly correlated (r = 0.95; P less than .01). We have characterized the inhibitory potency of a variety of 5-HT-antagonists against the stimulation of PI turnover elicited by 5-HT. Classic 5-HT2 antagonists mianserin, ketanserin, metergoline and pizotifen were found to inhibit this response in the low nanomolar range; amitryptiline and haloperidol were 10- to 20-fold less potent. The alpha-1 receptor antagonist, prazosin, was inactive in micromolar concentrations. The potency of the 5-HT2 antagonists was correlated with their ability to displace [3H] ketanserin binding from rat frontal cortex membranes (r = 0.90; P less than .05). The tumor promoter phorbol dibutyrate was found to inhibit 5-HT-stimulated PI turnover at low nanomolar concentrations whereas the biologically inactive substance 4-alpha-phorbol was ineffective. Pretreatment of rat aorta with phorbol dibutyrate at concentrations that inhibited 5-HT-induced PI turnover also attenuated the aortic contraction induced by 5-HT in the presence of a calcium channel blocker nitrendipine. Our results suggest that phorbol esters may desensitize 5-HT2-receptor-mediated PI turnover and contraction of rat aorta, possibly via an activation of protein kinase C.

Animals↗
PubMed1986

Detection and characterization of beta-adrenergic receptors and adenylate cyclase in coated vesicles isolated from bovine brain.

To assess whether internalization of beta-adrenergic receptor occurs in the CNS, we have isolated clathrin-coated vesicles from bovine forebrain and examined them for the presence of beta-adrenergic receptor binding and adenylate cyclase activities. A coated vesicle enriched preparation isolated by successive D2O-Ficoll density gradient centrifugations was applied to a glass bead permeation column to achieve further purification. Two major peaks of protein were eluted from the column and monitored by electron microscopy and SDS-PAGE. Peak II contained almost exclusively coated vesicles (98%), whereas peak I, which appeared in the void volume, contained larger smooth vesicles and few coated vesicles. beta-Adrenergic receptor binding to peaks I and II was measured with 125I-cyanopindolol (CYP) as ligand in Sepharose 4B column assays. 125I-CYP was found to bind specifically and saturably to both peaks I and II with a Bmax of 28 +/- 4 and 32 +/- 3 fmol/mg protein, respectively. 3H-CGP 12177, a hydrophilic beta-adrenergic receptor ligand, did not label receptors present in peak II, but it specifically bound to synaptic plasma membranes (SPM) prepared from bovine hippocampus and, to a lesser extent, to peak I. These results suggest that receptors present in coated vesicles are cryptic in nature. In the displacement of 125I-CYP binding by (-)-isoproterenol, addition of 50 microM GppNHp caused a significant "right shift" with SPM and peak I but not the peak II preparation. Adenylate cyclase activities could also be detected in both peaks I and II (specific activities, 21 +/- 0.6 and 24 +/- 0.5 pmol cAMP/mg protein/min, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclases↗
PubMed1985

5-Hydroxytryptamine uptake and imipramine binding sites in neurotumor NCB-20 cells.

NCB-20 cells (neuroblastoma X fetal Chinese hamster brain hybrids) are equipped with a [3H]5-hydroxytryptamine [( 3H]5-HT) uptake system and [3H]imipramine recognition sites. Approximately 80% of the radioactivity taken up by cells incubated with [3H]5-HT was identified with 5-HT. [3H]5-HT uptake was temperature-dependent, partially sodium-dependent, saturable (Km = 7.3 +/- 0.6 microM; Vmax = 2.0 +/- 0.6 pmol/min/mg), and inhibited by clomipramine, imipramine, fluoxetine, and desipramine, but not by iprindole, mianserin, or opipramol. Lineweaver-Burk plots showed a competitive type of inhibition by imipramine and fluoxetine. [3H]5-HT uptake was not inhibited by nisoxetine or benztropine. [3H]Imipramine binding sites had a KD of 12 +/- 2 nM and a Bmax of 22 +/- 7 pmol/mg protein. The binding was sodium-sensitive although to a lesser extent than that found with brain membranes. Imipramine binding was displaced by tricyclic antidepressants with the following order of potency: clomipramine greater than imipramine greater than fluoxetine greater than desipramine much greater than iprindole = mianserin greater than opipramol. These results suggest that imipramine binding sites are present together with the 5-HT uptake sites in NCB-20 cells and that these sites interact functionally but are different biochemically.

Animals↗
PubMed1985

Phasic and tonic components in 5-HT2 receptor-mediated rat aorta contraction: participation of Ca++ channels and phospholipase C.

The mechanisms of 5-hydroxytryptamine (5-HT)-induced contraction of rat aorta were investigated in vitro. The 5-HT-induced contraction could be analyzed into two distinct components (phasic and tonic) by the use of appropriate inhibitors; nifedipine, an inhibitor of voltage-dependent Ca++ channels, inhibited only the phasic component of 5-HT-induced contraction while totally blocking the KCl-induced contraction. 2-Nitro-4-carboxyphenyl-N,N-diphenylcarbamate, an inhibitor of phospholipase C, inhibited the tonic components of 5-HT-induced contraction as well as the 5-HT-induced stimulation of phosphoinositide hydrolysis in rat aorta. This component of contraction was mimicked by a protein kinase C activator 12-O-tetradecanoylphorbol-13-acetate. These results suggest that 5-HT2 receptors differentially regulate a voltage-dependent Ca++ channel and phospholipase C activity; the voltage-dependent Ca++ channel is involved in the phasic component of contraction whereas the phosphoinositide hydrolysis that results in the activation of protein kinase C and calcium mobilization by inositol triphosphate plays a physiologically important role in the tonic component of the aortic contraction.

Animals↗
PubMed1985

Stereospecific opiate-binding sites occur in coated vesicles.

We prepared clathrin-coated vesicles from bovine forebrain utilizing sucrose or deuterium oxide-Ficoll density gradient centrifugation followed by permeation chromatography. Homogeneity was monitored by electron microscopy (EM) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). EM revealed that the predominant (up to 98% of the total) organelles were coated vesicles and empty hexagonal baskets. Diameters of the coated vesicles ranged from 37 to 120 nm with a mean of 65.2 +/- 2.2. Upon SDS-PAGE of the coated vesicle fraction, the most prominent band appeared at 180,000 daltons. There were also three additional bands at 100,000, 50,000 and 35,000 daltons, giving the overall pattern characteristic of coated vesicles. Both 0.5 nM tritiated naltrexone and etorphine displayed specific binding to coated vesicles. Naltrexone binding in coated vesicles from gradient fractions was increased 2.5-fold over the original 100,000 X g pellet. An additional 4-fold enrichment in specific binding was observed after permeation chromatography which was concomitant with an increase in the volume density of coated vesicles in electron micrographs. Naltrexone binding was stereospecific and etorphine binding was inhibited by 100 mM NaCl (40%). Both naltrexone and etorphine binding were inhibited by 50 microM guanyl-5'-yl imidodiphosphate (40 to 50%). In summary, purified bovine brain-coated vesicles contained high affinity stereospecific opiate alkaloid-binding sites with characteristic opioid binding properties.

Animals↗
PubMed1985

Differential ontogeny of multiple opioid receptors (mu, delta, and kappa).

We investigated the postnatal ontogeny of opioid receptors in rat brain under assay conditions which, when combined with computerized analysis, effectively reflect the developmental profile of high affinity binding to mu, delta, and kappa subpopulations. Concentrations of mu sites were assessed with the selective ligand 3H-[D-ala2,mePhe4,gly-ol5]enkephalin (DAGO). The other two sites were analyzed in binding assays with less selective radioligands but in the presence of specific unlabeled ligands which suppress cross-reactivity. We utilized 3H-[D-ala2,D-leu5]enkephalin (DADL) in the presence of 10 nM DAGO to label delta sites and 3H-ethylketocyclazocine (EKC) in the presence of 100 nM DADL + 100 nM [D-ala2,mePhe4,Met(0)ol5]enkephalin to detect kappa receptors. After birth, the density (femtomoles per milligram of wet weight) of mu sites declined for several days and then rose sharply over the next 2 weeks, increasing 2-fold by adulthood. Delta (delta) sites appeared in the second week postnatal and increased more than 8-fold in the next 2 weeks. Levels of kappa receptors were relatively low at birth and increased slowly (2-fold, overall). Computerized analyses of binding data revealed that DAGO and DADL were binding to single populations of sites throughout the postnatal period. DAGO and EKC affinities did not fluctuate in this period, whereas DADL affinities were low for the first week and then rose to adult levels. In summary, mu, kappa, and delta receptors exhibit differential postnatal developmental profiles. The former two are present at birth, whereas the latter appears in the second week. The postnatal increase for all three sites appear to be preceded by the previously demonstrated emergence of opioid peptides.

Animals↗
PubMed1985

Evidence for an endacoid for the 5HT2 recognition site.

A peptide was partially purified from bovine forebrain which specifically inhibits the binding of [3H]-ketanserin to the 5HT2 recognition site. The peptide has a MW of approximately 6,000 daltons and is partially destroyed by limited proteolysis. We suggest that the peptide is a candidate for an endacoid for the 5HT2 recognition site.

Animals↗
PubMed1984

Kinetic evidence for differential agonist and antagonist binding to bovine hippocampal synaptic membrane opioid receptors.

To examine the kinetics of opioid receptor binding, the agonists [D-Ala2-D-Leu5]enkephalin (DADL) and [D-Ala2-MePhe4-Gly-ol5]enkephalin (DAGO) and the antagonists diprenorphine and naltrexone were used with bovine hippocampal synaptic plasma membranes. By computer modeling of equilibrium binding displacement curves utilizing the LIGAND program, we found opioid peptides bind with high affinity to single populations of synaptic plasma membranes receptors, whereas opiate alkaloids bind to multiple sites. Initial kinetic experiments revealed that agonist rates of association were radioligand concentration-independent. Pseudo first-order rate constants for DADL, DAGO, diprenorphine, and naltrexone association were estimated to be 5.63 X 10(5), 5.08 X 10(5), 4.60 X 10(6), and 2.3 X 10(6) mol-1 X s-1, respectively. After preincubation of 0.2-1 nM radioligand for variable time intervals, dissociation was initiated by addition of 1 microM unlabeled ligand. If saturation binding was achieved before dissociation was initiated, then nearly monophasic dissociation of DADL, DAGO, and diprenorphine and a biphasic off-rate for naltrexone were observed. When association times were reduced to pre-equilibrium intervals, the kinetics of dissociation of agonists became biphasic and association time-dependent, but that for antagonists did not change significantly. Comparisons by both graphical methods and computerized nonlinear regression analyses of rate constants revealed that the fraction of the rapid component of agonist dissociation decreases and that of the slow component is elevated with increasing receptor occupancy. In the presence of 100 mM NaCl, DADL dissociation became association time-independent. These data are consistent with the idea that the Na+ effect is brought about by a change of receptor to an antagonist-like conformation. On the basis of both association and dissociation kinetic data, opioid agonists appear to interact in a multistep process in which a rapid, reversible association is followed by the formation of a more tightly bound complex.

Animals↗