Alteration of contractile function and calcium ion movements in vascular smooth muscle by gentamicin and other aminoglycoside antibiotics

Experiments were conducted to examine the effects of certain aminoglycoside antibiotics on contractile responses and related calcium ion (Ca(2+)) movements in isolated vascular smooth muscle. Gentamicin, kanamycin, and streptomycin decreased contractile responses produced by norepinephrine, histamine, and high K(+) in rabbit aortic strips. The inhibitory action of these antibiotics on mechanical function was more pronounced when the Ca(2+) concentration of the bathing solution was decreased from 1.5 mM (normal Ca(2+) solution) to 0.05 mM (low Ca(2+) solution). The uptake of radiocalcium ((45)Ca) into the isolated media-intimal layer of rabbit aortae was decreased in a maintained manner by each antibiotic. With gentamicin, the inhibitory effect on (45)Ca uptake was shown to be dependent upon the concentration of gentamicin employed and to be more evident in a 0.1 mM Ca(2+) solution than in a normal Ca(2+) solution. In addition, the rate of (45)Ca efflux from the rabbit aortic media-intimal layer was increased in a sustained manner by gentamicin, streptomycin, and kanamycin. Furthermore, contractile responses induced by high K(+) and norepinephrine in canine carotid arterial strips were inhibited by gentamicin. Present findings indicate that aminoglycoside antibiotics interfere with Ca(2+)-linked events leading to activation of the contractile mechanism of vascular smooth muscle. These in vitro findings may partially explain the occurrence of in vivo cardiovascular depression that has occasionally been observed after the administration of chemically related antimicrobial agents.

Increased nuchal translucency and split-hand/foot malformation in a fetus with an interstitial deletion of chromosome 2q that removes the SHFM5 locus

OBJECTIVES

To describe and discuss the clinical, cytogenetic and molecular findings in a fetus with the first prenatally detected interstitial deletion of chromosome 2q.

CASE REPORT

A fetus with increased nuchal translucency on routine ultrasound examination at 13 weeks' gestation was found to have severe upper-limb abnormalities on follow-up ultrasound examination at 16 weeks. The pregnancy was terminated, and the autopsy revealed monodactyly of the right upper limb, oligodactyly of the left upper limb and bilateral split foot, as well as atrial and ventricular septal defects and mild facial dysmorphism.

RESULTS

Cytogenetic studies and haplotype analysis of the fetus and both parents showed that the fetus carried a de novo deletion encompassing a region of about 30 Mb on the paternal chromosome 2q (karyotype 46,XX,del(2)(q24.2-q32.2)).

CONCLUSION

This is the first instance of increased nuchal translucency associated with a chromosome 2q deletion. Moreover, the striking malformations affecting all four of the fetus' limbs support previous suggestions that a novel locus for split-hand/foot malformation (SHFM5) lies on chromosome 2q31.

A locus for asphyxiating thoracic dystrophy, ATD, maps to chromosome 15q13

Asphyxiating thoracic dystrophy (ATD), or Jeune syndrome, is a multisystem autosomal recessive disorder associated with a characteristic skeletal dysplasia and variable renal, hepatic, pancreatic, and retinal abnormalities. We have performed a genome wide linkage search using autozygosity mapping in a cohort of four consanguineous families with ATD, three of which originate from Pakistan, and one from southern Italy. In these families, as well as in a fifth consanguineous family from France, we localised a novel ATD locus (ATD) to chromosome 15q13, with a maximum cumulative two point lod score at D15S1031 (Zmax=3.77 at theta=0.00). Five consanguineous families shared a 1.2 cM region of homozygosity between D15S165 and D15S1010. Investigation of a further four European kindreds, with no known parental consanguinity, showed evidence of marker homozygosity across a similar interval. Families with both mild and severe forms of ATD mapped to 15q13, but mutation analysis of two candidate genes, GREMLIN and FORMIN, did not show pathogenic mutations.

A novel acropectoral syndrome maps to chromosome 7q36

F syndrome (acropectorovertebral syndrome) is a dominantly inherited skeletal dysplasia affecting the hands, feet, sternum, and lumbosacral spine, which has previously been described in only two families. Here we report a six generation Turkish family with a related but distinct dominantly inherited acropectoral syndrome. All 22 affected subjects have soft tissue syndactyly of all fingers and all toes and 14 also have preaxial polydactyly of the hands and/or feet. In addition, 14 have a prominent upper sternum and/or a blind ending, inverted U shaped sinus in the anterior chest wall. Linkage studies and haplotype analysis carried out in 16 affected and nine unaffected members of this family showed that the underlying locus maps to a 6.4 cM interval on chromosome 7q36, between EN2 and D7S2423, a region to which a locus for preaxial polydactyly and triphalangeal thumb-polysyndactyly has previously been mapped. Our findings expand the range of phenotypes associated with this locus to include total soft tissue syndactyly and sternal deformity, and suggest that F syndrome may be another manifestation of the same genetic entity. In mice, ectopic expression of the gene Sonic hedgehog (Shh) in limb buds and lateral plate mesoderm during development causes preaxial polydactyly and sternal defects respectively, suggesting that misregulation of SHH may underlie the unusual combination of abnormalities in this family. A recently proposed candidate gene for 7q36 linked preaxial polydactyly is LMBR1, encoding a novel transmembrane receptor which may be an upstream regulator of SHH.

Human HOX gene mutations

HOX genes play a fundamental role in the development of the vertebrate central nervous system, axial skeleton, limbs, gut, urogenital tract and external genitalia, but it is only in the last 4 years that mutations in two of the 39 human HOX genes have been shown to cause congenital malformations; HOXD13, which is mutated in synpolydactyly, and HOXA13, which is mutated in Hand-Foot-Genital syndrome. Here we review the mutations already identified in these two genes, consider how these mutations may act, and discuss the possibility that further mutations remain to be discovered both in developmental disorders and in cancer.

Physical map of a 1.5 mb region on 12p11.2 harbouring a synpolydactyly associated chromosomal breakpoint

Synpolydactyly (SPD) is a rare malformation of the distal limbs known to be caused by mutations in HOXD13. We have previously described a complex form of SPD associated with synostoses in three members of a Belgian family, which co-segregates with a t(12;22)(p11.2;q13.3) chromosomal translocation. The chromosome 12 breakpoint of this translocation maps to 12p11.2 between markers D12S1034 and D12S1596. Here we show that a mutation in the HOXD13 gene is not responsible for the phenotype, and present a physical map of the region around the 12p11.2 breakpoint. Starting from D12S1034 and D12S1596, we have established a contig approximately 1.5 Mb in length, containing 13 YAC clones, 16 BAC clones, and 11 cosmid clones. FISH analysis shows that cosmid LL12NCO1-149H4 maps across the breakpoint, and Southern blot experiments using fragments of this cosmid as probes identify a rearranged BamHI fragment in the patients carrying the translocation. A search for expressed sequences within the contig have so far revealed one CpG island, seven anonymous ESTs and three previously characterised genes, DAD-R, KRAG and HT21, all of which were found not to be directly disrupted by the translocation. The gene represented by EST R72964 was found to be disrupted by the translocation. These findings lay the groundwork for further efforts to characterise a gene critical for normal distal limb development that is perturbed by this translocation.

Novel HOXA13 mutations and the phenotypic spectrum of hand-foot-genital syndrome

Hand-foot-genital syndrome (HFGS) is a rare, dominantly inherited condition affecting the distal limbs and genitourinary tract. A nonsense mutation in the homeobox of HOXA13 has been identified in one affected family, making HFGS the second human syndrome shown to be caused by a HOX gene mutation. We have therefore examined HOXA13 in two new and four previously reported families with features of HFGS. In families 1, 2, and 3, nonsense mutations truncating the encoded protein N-terminal to or within the homeodomain produce typical limb and genitourinary abnormalities; in family 4, an expansion of an N-terminal polyalanine tract produces a similar phenotype; in family 5, a missense mutation, which alters an invariant domain, produces an exceptionally severe limb phenotype; and in family 6, in which limb abnormalities were atypical, no HOXA13 mutation could be detected. Mutations in HOXA13 can therefore cause more-severe limb abnormalities than previously suspected and may act by more than one mechanism.

Sacral dysgenesis associated with terminal deletion of chromosome 7q: a report of two families

Most cases of sacral dysgenesis are considered to be sporadic events. We present two families in whom the presence of associated clinical features prompted specific investigation of chromosome 7, leading to the identification of an underlying chromosome 7q deletion causing sacral dysgenesis. All affected individuals had microcephaly and developmental delay. Detailed cytogenetic studies confirmed that all three affected individuals had a deletion of chromosome 7q associated with their sacral dysgenesis, developmental delay and related problems. The three affected patients were studied clinically, radiologically and cytogenetically. Eleven unaffected individuals from the two families were also investigated by genetic studies, specifically evaluating chromosome 7.

CONCLUSION

It is important that detailed family history, evaluation of associated malformations and the overall clinical picture be considered in identifying the underlying diagnosis in cases of anal stenosis/sacral agenesis. The cases we present demonstrate the value of detailed chromosome studies in such situations.

Acromelic frontonasal dysostosis

We report on 3 male and 2 female infants with acromelic frontonasal dysostosis. All 5 had a frontonasal malformation of the face and nasal clefting associated with striking symmetrical preaxial polysyndactyly of the feet and variable tibial hypoplasia. In contrast, the upper limbs were normal. This rare variant of frontonasal dysplasia may represent a distinct autosomal-recessive disorder. We suggest that the molecular basis of this condition may be a perturbation of the Sonic Hedgehog (SHH) signalling pathway, which plays an important part in the development of the midline central nervous system/craniofacial region and the limbs.

Heterozygous mutations in the gene encoding noggin affect human joint morphogenesis

The secreted polypeptide noggin (encoded by the Nog gene) binds and inactivates members of the transforming growth factor beta superfamily of signalling proteins (TGFbeta-FMs), such as BMP4 (ref. 1). By diffusing through extracellular matrices more efficiently than TGFbeta-FMs, noggin may have a principal role in creating morphogenic gradients. During mouse embryogenesis, Nog is expressed at multiple sites, including developing bones. Nog-/- mice die at birth from multiple defects that include bony fusion of the appendicular skeleton. We have identified five dominant human NOG mutations in unrelated families segregating proximal symphalangism (SYM1; OMIM 185800) and a de novo mutation in a patient with unaffected parents. We also found a dominant NOG mutation in a family segregating multiple synostoses syndrome (SYNS1; OMIM 186500); both SYM1 and SYNS1 have multiple joint fusion as their principal feature. All seven NOG mutations alter evolutionarily conserved amino acid residues. The findings reported here confirm that NOG is essential for joint formation and suggest that NOG requirements during skeletogenesis differ between species and between specific skeletal elements within species.

Mutation and deletion of the pseudoautosomal gene SHOX cause Leri-Weill dyschondrosteosis

Leri-Weill Dyschondrosteosis (LWD; OMIM 127300) is a dominantly inherited skeletal dysplasia characterized by disproportionate short stature with predominantly mesomelic limb shortening. Expression is variable and consistently more severe in females, who frequently display the Madelung deformity of the forearm (shortening and bowing of the radius with dorsal subluxation of the distal ulna). The rare Langer Mesomelic Dysplasia (LD; OMIM 249700), characterized by severe short stature with hypoplasia/aplasia of the ulna and fibula, has been postulated to be the homozygous form of LWD (refs 4-6). In a six-generation pedigree with LWD, we established linkage to the marker DXYS6814 in the pseudoautosomal region (PAR1) of the X and Y chromosomes (Z max=6.28; theta=0). Linkage analysis of three smaller pedigrees increased the lod score to 8.68 (theta=0). We identified submicroscopic PAR1 deletions encompassing the recently described short stature homeobox-containing gene SHOX (refs 7,8) segregating with the LWD phenotype in 5 families. A point mutation leading to a premature stop in exon 4 of SHOX was identified in one LWD family.

Synpolydactyly phenotypes correlate with size of expansions in HOXD13 polyalanine tract

Synpolydactyly (SPD) is a dominantly inherited congenital limb malformation. Typical cases have 3/4 finger and 4/5 toe syndactyly, with a duplicated digit in the syndactylous web, but incomplete penetrance and variable expressivity are common. The condition has recently been shown to be caused by expansions of an imperfect trinucleotide repeat sequence encoding a 15-residue polyalanine tract in HOXD13. We have studied 16 new and 4 previously published SPD families, with between 7 and 14 extra residues in the tract, to analyze the molecular basis for the observed variation in phenotype. Although there is no evidence of change in expansion size within families, even over six generations, there is a highly significant increase in the penetrance and severity of phenotype with increasing expansion size, affecting both hands (P = 0.012) and feet (P < 0. 00005). Affected individuals from a family with a 14-alanine expansion, the largest so far reported, all have a strikingly similar and unusually severe limb phenotype, involving the first digits and distal carpals. Affected males from this family also have hypospadias, not previously described in SPD, but consistent with HOXD13 expression in the developing genital tubercle. The remarkable correlation between phenotype and expansion size suggests that expansion of the tract leads to a specific gain of function in the mutant HOXD13 protein, and has interesting implications for the role of polyalanine tracts in the control of transcription.

Effects of two nonsulfhydryl angiotensin-converting enzyme inhibitors, CGS 14831 and CGS 16617, on myocardial damage and left-ventricular hypertrophy following coronary artery occlusion in the rat

The present study was designed to examine the effects of two new angiotensin-converting enzyme (ACE) inhibitors, CGS 14831 and CGS 16617 (3 mg/kg i. v. 1 min prior to occlusion and 4 and 24 h after occlusion), on myocardial ischemic (MI) damage and left-ventricular hypertrophy in rats. Administration of CGS 14831 or CGS 16617 inhibited angio-tensin-I-induced pressor responses by 40-100% for 4 h after each dose. Myocardial creatine phosphokinase (CK) levels were 10.6 +/- 0.6 U/mg protein in sham-MI animals, and following coronary artery occlusion for 48 h were decreased to 4.1 +/- 0.2 U/mg protein in MI + vehicle animals (p less than 0.01). CGS 14831 and CGS 16617 attenuated the decrease in CK content and resulted in 47 and 40% sparing, respectively, of the left-ventricular free wall. Neither agent attenuated the left-ventricular hypertrophy which developed following coronary artery occlusion. These data indicate that the nonsulfhydryl ACE inhibitors CGS 14831 and CGS 16617 have a significant cardioprotective effect in rats surviving 48 h, and suggest a potential therapeutic usefulness of these agents for the treatment of ischemia-induced heart failure.

Pharmacological characterization of CGS 15943A: a novel nonxanthine adenosine antagonist

CGS 15943A is a potent adenosine receptor antagonist with a novel nonxanthine heterocyclic ring structure. In vitro, CGS 15943A competitively inhibited the 2-chloroadenosine-induced A2 receptor-mediated relaxation of dog coronary artery strips contracted with KCl (25 mM). Similarly, CGS 15943A blocked 2-chloroadenosine- and N-ethylcarboxamideadenosine-induced A2 receptor-mediated relaxation of histamine-contracted guinea pig tracheal strips. Schild analysis of these results yielded pA2 values of 10.8 and 10.1 for the coronary arteries and the tracheal smooth muscle strips, respectively. In comparison, 8-phenyltheophylline blocked 2-chloroadenosine-induced tracheal response with a pA2 value of 7.0. CGS 15943A was devoid of intrinsic activity, and did not affect either histamine- or KCl-induced contractions of the smooth muscle strips. In the electrically stimulated guinea pig left atrial preparation, CGS 15943A antagonized the A1 receptor-mediated negative inotropic effects of R-phenylisopropyladenosine with a pA2 value of 7.4. In vivo, i.v. administration of CGS 15943A blocked the vasodepressor response to 2-chloradenosine in anesthetized normotensive rats with an ID50 of 0.024 mg/kg. In addition, p.o. administration of CGS 15943A (4.0 mg/kg) to conscious rats inhibited 2-chloroadenosine-induced decreases in diastolic blood pressure; maximal effects were observed 30 min after dosing, with a T1/2 of approximately 103 min. Therefore suggesting that CGS 15943A is an orally active antagonist of adenosine receptors. These results indicate that CGS 15943A antagonized both A1 and A2 receptor-mediated responses with a greater affinity toward the A2 than the A1 receptor subtype.

Differential calcium movements induced by agonists in guinea pig tracheal muscle

The effects of high potassium, carbachol and histamine on tension responses and 45Ca fluxes in tracheal smooth muscle were examined. Calcium depletion or nitrendipine (10(-8) M) inhibited potassium-induced contractile responses more than those obtained with either histamine or carbachol, whereas Sr2+ inhibited mainly responses to histamine or carbachol. The Ca2+ entry facilitator, CGP 28392 (3 X 10(-6) M), potentiated contractions induced only by potassium. Uptake of 45Ca in guinea pig tracheal muscle can be separated into high and low affinity components. The 45Ca efflux rate from tracheal muscle into a La3+-substituted solution was over four-fold higher than in other smooth muscles. Potassium, carbachol and histamine induced sustained increases in 45Ca efflux into solutions containing 1.5 mM Ca2+; only transient increases in 45Ca efflux with carbachol and histamine were obtained after Ca2+ depletion. These agonists elicit contractile responses in tracheal muscle by selectively mobilizing different cellular and extracellular Ca2+ components.

Central and peripheral inhibition of angiotensin converting enzyme (ACE) in the SHR: correlation with the antihypertensive activity of ACE inhibitors

A series of five structurally distinct ACE inhibitors were evaluated for their ability to inhibit tissue ACE activity in the SHR after oral administration. In the first series of experiments, the ACE inhibitors captopril, enalapril, pentopril, CGS 14824A and CGS 16617 were given to groups of SHR at doses that produced a 15 to 20 mm Hg reduction in blood pressure within 1 hour. Under these conditions of dose and time, only captopril significantly inhibited brain ACE activity (43%), whereas inhibition of serum ACE activity ranged from 72% to 99% with these agents. Inhibition of aortic ACE activity ranged from 54% to 87%, and lung ACE inhibition varied from 50% to 83%. In the second series of experiments, SHR were administered higher doses of each ACE inhibitor such that these compounds produced peak reductions in blood pressure (-25 mm Hg to -33 mm Hg) within a range of 2 to 6 hours. When tissue ACE activity was measured at the time corresponding to peak reduction in blood pressure, all five ACE inhibitors produced a significant inhibition of brain ACE activity ranging from 21% to 76%. Serum ACE activity was almost completely inhibited by these agents, with the exception of captopril (62% inhibition). The inhibition of aortic ACE activity ranged from 79% to 99%, while the inhibition of lung ACE activity did not increase under these conditions. These data suggest that ACE inhibitors may exert their maximal antihypertensive effects by inhibiting ACE in vascular tissues and brain.

Relationship between 45Ca movements, different calcium components and responses to acetylcholine and potassium in tracheal smooth muscle

Correlations between tension responses elicited with acetylcholine (ACh) and high K+ and corresponding alterations in Ca++ mobilization were obtained in rabbit and canine tracheal smooth muscle. Removal of Ca++ or preincubation with D-600 (50 microM) inhibited responses to K+ (50 or 80 mM) and low ACh (89 nM) and had only a small effect on responses to high ACh (8.9 microM). Conversely, solutions containing Sr++ instead of Ca++ inhibited responses to both concentrations of ACh to a greater degree than were those to K+. Washout of slow component 45Ca into a O-Ca solution was more rapid in rabbit trachea than reported previously for rabbit aorta. Washout of tracheal smooth muscle into an 80.8 mM La -substituted solution at 0.5 degrees C removed superficial (La -accessible) 45Ca and blocked both 45Ca uptake and most 45Ca efflux. D-600, which had no significant effect on control 45Ca uptake in rabbit aortic smooth muscle, decreased 45Ca uptake by 33% in rabbit tracheal smooth muscle. The uptake of 45Ca from the Ca++ binding sites with low affinity for Ca++ was increased by 80 mM K+, 50 mM K+ or 8.9 microM ACh, and the accumulation of Ca++ from the Ca++ binding sites with high affinity for 45Ca was inhibited by Sr++. The stronger effect of either Ca++ removal or D-600 on responses to K+ and the correspondingly greater effect of Sr++ on responses to ACh indicate that different Ca++ stores are present in tracheal smooth muscle. These Ca++ components appear to be qualitatively similar to those present in aortic smooth muscle but they differ quantitatively and are not as readily dissociated as are aortic Ca++ components.

A comparative study of the respiratory responses to bronchoactive agents in rhesus and cynomolgus monkeys

Respiratory responses to a variety of known bronchoactive agents were compared in anesthetized rhesus (Macaca mulatta) and cynomolgus (Macaca fascicularis) monkeys. Administration of 0.1 to 1.0% histamine aerosols resulted in an increase in airway resistance of 50 to 200% and a decrease in lung compliance of 30 to 80%. Aerosols of prostaglandin E2 (1 mg/ml), terbutaline (10 mg/ml), and isoproterenol (10 mg/ml) or iv aminophylline (up to 7.0 mg/kg) administered concomitantly with histamine produced a transient reversal of the histamine-induced changes in both species. Since the rhesus and cynomolgus monkeys responded in a comparable manner to these bronchodilator agents, the cynomolgus monkey appears to be an additional valuable model for the evaluation of potential bronchoactive compounds.

Respiratory responses to Ascaris antigen in rhesus and cynomolgus monkeys

Responses to Ascaris antigen were evaluated in rhesus and cynomolgus monkeys. Of 19 cynomolgus monkeys tested, 15 were found to have cutaneous reactivity to Ascaris: 13 of these responded to Ascaris aerosols with changes in respiratory function including an increase in respiration rate, decrease in tidal volume and peak expiratory flow rate, decrease in dynamic compliance, and an increase in resistance. Four of the six rhesus monkeys studied with cutaneous reactivity to Ascaris responded to Ascaris aerosols: the changes in respiratory function observed after the Ascaris challenge in these monkeys were similar to those observed in the cynomolgus monkeys. Responses to repetitive Ascaris challenges were obtained in monkeys of both species with a recovery period of 30 to 60 min between challenges. In monkeys of both species that reacted to Ascaris aerosols, blood pressure was elevated transiently; changes in heart rate were variable. Changes in cardiovascular measurements were not observed in monkeys that did not respond to Ascaris aerosols. Thus, it appears that the cynomolgus monkey responds to an aerosol Ascaris challenge in a manner similar to the rhesus monkey and is an additional suitable model for the study of allergic respiratory responses.

Evaluation of rotenone and related compounds as antagonists of slow-reacting substance of anaphylaxis

Rotenone (1), dihydrorotenone (2), isorotenone (3), mutarotenone (4), and deguelin (12) were found to be potent antagonists of slow-reacting substance of anaphylaxis (SRS-A) in vitro. However, these compounds were also shown to inhibit histamine, serotonin, and acetylcholine at only ten times their IC50 concentrations for SRS-A antagonism. Rotenone (1) and several related compounds were also evaluated in an in vivo guinea pig anaphylaxis model. Several of these compounds and FPL 55712 (I) were effective in prolonging collapse times of animals which received an aerosol challenge of an antigen to which they had been sensitized.

Delta-9-tetrahydrocannabinol on isolated human bronchioles

Experiments were conducted to investigate the bronchodilating action of delta-9-tetrahydrocannabinol (THC) using normal human lung tissue obtained post mortem. Isolated rings of human bronchioles contracted to histamine, carbachol, and prostaglandin F(2a)(PGF(2a)) and relaxed to isoproterenol. THC (5 X 10(-4)M) did not alter the responses of the bronchial rings to histamine, whereas methapyrilene (10(-6)M) antagonized these responses. Atropine (2 X 10(-6)M) had a highly significant effect on the responses of the bronchioles to carbachol: there was also a significant effect of THC (5 X 10(-4)M), but to a much lesser extent than atropine. Propranolol (10(-6)M) pretreatment significantly antagonized the relaxant responses of the bronchioles to isoproternol: THC antagonized these responses to a smaller degree. Incubation with THC did not cause relaxation of resting tissues or tissues in which a spasm had been induced. These data suggest that THC does not have significant direct effects in human bronchial smooth muscle and that bronchoactivity observed in vivo is likely to be of a nondirect or central origin.

Effects of hypertonic mannitol on contractile responses and 45Ca movements in isolated canine arteries

The effects of hyperosmotic mannitol on vascular smooth muscle contractile responses and on 45Ca movements were examined in different isolated canine arteries. Prior exposure to 50 mM mannitol decreased contractile responses elicited with dopamine (DA) in helical strips of canine terminal mesenteric arteries (Tm) and decreased the contractile response elicited with potassium (K+) in both isolated left anterior descending (LAD) and circumflex coronary arteries. Tension responses induced by norepinephrine or DA in the Tm and K+ and prostaglandin F2 alpha in LAD were relaxed by subsequent exposure to mannitol. Mannitol increased the uptake of 45Ca in Tm arteries. Exposure of the Tm and branches of the LAD to mannitol during the washout of 45Ca resulted in a decrease in the rate of loss of 45Ca; the presence of either K+, Mg2+, or ethylenediamine tetraacetic acid during the washout did not prevent the observed mannitol-induced decrease in 45Ca efflux. These effects of mannitol on 45Ca efflux without a concomitant major change in net 45Ca uptake could be attributed to an increase in bound Ca2+ at relevant membrane sites or stores. Thus, hypertonic mannitol may alter contractile responsiveness of selected canine arteries by impeding the release of bound and/or sequestered Ca2+ and, in this manner, decreasing the Ca2+ concentration at the contractile elements.

Calcium incorporation by canine aortic smooth muscle microsomes

The accumulation of calcium (Ca2+) and factors influencing Ca2+ incorporation in vascular smooth muscle were examined in a microsomal fraction prepared from canine aortae. The accumulation of Ca2+ required the presence of ATP and increased over time. Furthermore, the incorporation of 45Ca into the microsomal preparation was stimulated both in the presence of oxalate and when the Ca2+ concentration of the bathing media was elevated from 20 micron to 40 micron. Calcium uptake (with oxalate) was temperature-dependent; uptake was unaffected by azide. Both lanthanum (La3+) and phosphatidyl serine (PS) inhibited ATP-dependent uptake in a concentration-dependent manner. In the presence of ATP, calcium binding (without oxalate) was slightly inhibited by La3+, whereas PS had no effect under these conditions. When ATP was removed from the incubation medium, the presence of PS stimulated both the uptake and binding of 45Ca, whereas La3+ decreased both uptake and binding. These findings support the idea that La3+ binds on the surface of the vesicles and, in this manner, decreases available Ca2+ sites, whereas PS appears to increase the number of Ca2+ sites by either entering the membranes or adsorbing on it.

Characteristics of 45Ca uptake and efflux in rat lung slices

The distribution and movements of 45Ca were investigated in lung slice preparations obtained from rats. The accumulation of 45Ca was measured in either 5.0 mM Ca2+, 0.5 mM Ca2+ or 0-Ca solutions. The 45Ca tissue to medium ratio was greatest in the 0-Ca solution; the presence of either 5.0 mM Ca2+ or 0.5 mM Ca2+ reduced this ratio 8- and 5-fold, respectively. Efflux of 45Ca indicated that there are at least two washout components. Exposure to either La3+ or Sr2+ (0.5 mM) during the washout resulted in a transient increase in 45Ca efflux (Sr2+ greater than La3+), whereas 0 degrees C slowed the loss of 45Ca. Uptake of 45Ca was increased by the metabolic inhibitor iodoacetic acid and inhibited in the presence of either La3+ or Sr2+. These findings indicate that the 45Ca accumulated within the lung is not readily depleted and a portion appears to accumulate at intracellular or less superficial sites or stores.

Effect of pulmonary edema on drug transport and binding in rat lung

The pulmonary absorption and uptake of (35S)phenol red ((35S)PR was measured in anesthetized rats with alpha-naphthylthiourea- (ANTU) induced lung edema. When (35S)PR solution was injected through a tracheal cannula in control animals and the percentage of the tracheal cannula in control animals and the percentage of the dose unabsorbed plotted semilogarithmically against time, an apparent first-order absorption rate was obtained. In contrast, in rats with ANTU-induced edema, the absorption time curve showed at least two different first-order components. Increasing the concentration of (35S)PR from 0.01 to 3 mM resulted in a decrease in the percentage absorption of the compound in controls compared with a relatively constant percentage absorption in edematous lungs. (35S)PR uptake by lung slices from ANTU-treated rats was decreased in the presence of IAA and a N2 atmosphere, and the dye accumulated at a faster rate and to a greater extent than in controls. The results suggest that although energy-dependent drug transport mechanisms remain intact, the porosity of the absorbing membranes and the extent of drug binding in the lung are increased markedly in the presence of edema.

Contractile function and 45Ca movements in vascular smooth muscle of nonhuman primates: effects of aminoglycoside antibiotics

1. The effects of 7mM neomycin, 10 mM kanamycin and 5 mM gentamicin on vascular smooth muscle contractile responses and 45Ca movements were examined in arterial preparations isolated from nonhuman primates (squirrel monkeys, capuchin monkeys and baboons). 2. Present findings demonstrate that these antibiotics inhibit contractile responses and alter 45Ca movements in monkey blood vessels, and suggest that the manner in which these agents affect vascular smooth muscle from nonhuman primates does not differ qualitatively from their effects in canine and rabbit vascular preparations.

Distribution of a lanthanide (147 Pm) in vascular smooth muscle

In order to ascertain whether trivalent rare earth ions such as lanthanum (La+++) penetrate the cell membrane under physiological conditions, the extracellular and cellular distribution of promethium (147 Pm), a carrier-free rare earth radioisotope, was examined in rabbit aortic smooth muscle. As the duration of incubation was lengthened, uptake of 147Pm continued to increase; it was inhibited by La+++ and other rare earth ions (Nd+++, Lu+++) only when the 147 Pm/rare earth concentration ratio exceeded 1:10(6). However, equally high concentrations of Ca++ had no effect on 147Pm uptake. Efflux of 147Pm was only transiently increased by 1.5 mM La+++, and exposure to 0.05 mM EDTA elicited an increased 147Pm efflux with both transient and maintained components. The magnitude of the EDTA-induced increase in 147 Pm efflux was similar over a 30-fold range of EDTA concentration (0.05-1.5 mM); the limiting factor for 147Pm efflux is the rate of 147Pm desorption from the tissue rather than the extracellular concentration of EDTA. Loss of 147Pm in the presence of 0.05 mM EDTA could be described in terms of two specific washout components (the more rapid of which included 147Pm within the extracellular space and the slower of which had half-times of washout of approximately 7-10 minutes). Uptake of 147Pm was inhibited by lowering the incubation solution temperature to 0 degrees C or by procaine. However, concentrations of metabolic inhibitors (iodoacetate and dinitrophenol) which diminish loss of Ca++ from the cell did not decrease either the uptake or efflux of 147Pm. Thus, significant quantities of 147Pm do not appear to be accumulated within the cell or transported out of the cell; distribution of 147Pm can be most simply described in terms of a binding at and desorption from surface acessible fiber sites.

Comparison of uptake and binding of disodium cromoglycate and phenol red in rat lung

In rat lung slices 3H-disodium cromoglycate (3H-DSCG) (0.001 mM) was taken up rapidly and 3H-DSCG tissue spaces, which equilibrated by 30 minutes, remained constant over a 4-hour incubation period. In contrast, 35S-phenol red (0.001 mM) accumulated in lung slices to a much greater extent than did DSCG, and the measured tissue spaces continued to increase over a 3-hour incubation period. In the presence of either phenol red (1 mM) or the metabolic inhibitors, iodoacetic acid (10(-4) M) and dinitrophenol (10(-4) M), 3H-DSCG uptake was significantly decreased. Accumulation of 3H-DSCG in lung slices and binding to tissue homogenates (pH 7.4) was also decreased when Ca and Mg ions were omitted from the bathing solution. Although DSCG and phenol red mutually inhibited the accumulation of one another over time in lung slices and 3H-DSCG (0.001 mM) binding to lung homogenates was decreased in the presence of 1 mM phenol red, 35S-phenol red efflux was not altered by the addition of 1 mM DSCG during the washout. Thus, it appears that, in rat lung, DSCG and phenol red share a common binding site(s) for uptake, possible on the transport "carrier." Also, there appear to be additional pulmonary binding sites for phenol red. These sites are not occupied by DSCG and their presence could account for the differences observed in the extent of accumulation of the two compounds in lung slices.

Alteration by phosphatidyl serine of tension responses and 45Ca distribution in aortic smooth muscle

The effects of phosphatidyl serine (PS) on 45Ca distribution, 45Ca movements and contractions were examined in rabbit aortic smooth muscle. Contractile responses to submaximal concentrations of norepinephrine and histamine were potentiated by prior exposure to PS, but equivalent responses to potassium were unaffected. Addition of PS to the incubation solution decreased 45Ca uptake; exposure of aortic strips to PS during washout of either 45Ca or promethium (147Pm) resulted in maintained increases in efflux. These PS-induced alterations in net loss of 45Ca or 147Pm can be attributed to a decreased membrane reuptake and/or rebinding. However, the presence of PS during the washout significantly reduced the increases in 45Ca efflux rate elicited with either 0.05 mM concentrations of Ca++ or ethylenediamine tetraacetic acid. Thus, in rabbit aortic smooth muscle, exogenous PS can alter the availability and/or exchangeability of a membrane-bound Ca++ fraction. By specifically increasing the affinity for Ca++ at relevant membrane sites or stores. PS may enhance the ability of vascular smooth muscle to respond to stimulatory agents that mobilize Ca++ from these sites and, in this manner, potentiate contractile responses.

Effects of metiamide on distribution of 14C-histamine in aortic smooth muscle

The effects of metiamide on 14C-histamine movements and on contractions induced by histamine were studied in rabbit aortic smooth muscle. Low temperature (0 degrees C) and pretreatment with aminoguanidine or chloroquine markedly reduced the uptake of 14C. Component analysis of 14C efflux curves indicated that this decrease occurred mainly within the slower of two washout components. Addition of metiamide (but not pyrilamine) to the bathing solution decreased 14C-histamine uptake, and exposure to metiamide during the washout of 14C-histamine decreased the rate of efflux. These effects of metiamide on 14C-histamine movements can be explained in terms of an altered ability of rabbit aortic smooth muscle to accumulate histamine at some cellular site or store.

Interactions between several rare earth ions and calcium ion in vascular smooth muscle

The effects of lutetium (Lu+++), europium (Eu+++) and neodymium (Nd+++) on 45Ca distribution, 45Ca movements and contractions were examined in rabbit aortic smooth muscle. Tension responses to norepinephrine were markedly inhibited by all three rare earth ions; K+-induced responses and those to histamine were partially blocked. Addition of 1.5 mM Lu+++, Eu+++ or Nd+++ to the bathing solution reduced 45Ca uptake (Nd+++ greater than Eu+++ greater than greater than Lu+++), produced a maintained increase in 45Ca efflux from strips of media-intimal layer washed out in a 0-Ca++ solution (Nd+++ greater than Eu+++ greater than Lu+++), and, when present during 45Ca incubation (before 45Ca washout), altered the release of 45Ca elicited by addition of 1.5 mM Ca++ during the 45Ca washout (inhibition by Nd+++ greater than Eu+++ greater than Lu+++). The 3-fold greater uptake of 45Ca in a 0-Ca++ and 1.5 mM Lu+++ solution than in an equivalent Sr++ solution results from a decreased effect of Lu+++ upon the slower 45Ca washout component. The actions of Lu+++ were quantitatively similar to those of low La+++ concentrations (0.05-0.10 mM), whereas those of Nd+++ and Eu+++ resembled effects obtained with equimolar concentrations of La+++. Thus, the three rare earth ions produce qualitatively similar alterations in 45Ca uptake and superficial binding. The difference observed can be attributed to variations in their affinity for superficial Ca++ binding sites and in their ability to block Ca++ uptake.

Differential inhibitory effect of neomycin on contractile responses of various canine arteries

The influence of neomycin on vascular smooth muscle contractile responses was examined in different isolated arterial preparations of the dog. Prior exposure (5 minutes) to 7 mM neomycin decreased contractile responses elicited with norepinephrine (NE, 0.6 muM) or KC1 (K-+, 80 nM) in helical strips of canine aortae (Ao) and femoral (F), carotid (Cd), renal (R), superior mesenteric (Sm), terminal mesenteric (Tm) and coronary (Cr) arteries. Addition of neomycin subsequent to NE-induced contractile responses depressed tension responses of the F, Cd, R, Sm and Tm arteries but had little or no effect on the Ao. However, after contractions had been elicited with K-+, neomycin had no effect on tension responses of the Ao, F, Cd, R or Sm arteries but depressed contractions of the Cr and Tm arterial strips. Preincubation with neomycin (0.7-3.5 mM) produced a concentration-related inhibition of contractile responses elicited in Tm arterial strips by addition of calcium ions (Ca-++; 1.6 mM) to a Ca-++-free depolarizing solution; conversely, subsequent addition of neomycin had no effect on maintained Ca-++ contractures. In constant flow-perfused terminal mesenteric arterial branches, neomycin (0.5-4.0 mM) produced a concentration-related antagonism of pressor responses elicited with NE (1-8 mug) or K-+ (40 mM). The inhibitory action of neomycin on K-+-induced pressor responses was inversely related to the Ca-++ concentration of the perfusion fluid. However, inhibition of NE pressor responses by neomycin did not appear to be related to the Ca-++ concentration. The differential inhibitory action of neomycin on contractions induced by NE and K-+ in various canine arteries suggests that different vascular beds vary in the manner in which Ca-++ is bound and subsequently utilized by stimulatory agents to elicit tension changes.

Effects of neomycin on 45Ca binding and distribution in canine arteries

The effects of neomycin (7.0 mM) on 45Ca movements and distribution were investigated in canine aortae and in canine carotid and terminal mesenteric arteries. Uptake of 45Ca was measured in calcium-free solution; the 45Ca tissue spaces in the carotid and terminal mesenteric arteries were 2--4 times greater than those observed in the aorta. Exposure of the aortae and the terminal mesenteric arteries to 1.5 mM Ca++ during the washout elicited large increases in 45Ca efflux in both preparations (increase in terminal mesenteric greater than aorta). Moreover, in all three arterial preparations, neomycin reduced 45Ca uptake and induced a sustained increase in 45Ca efflux (effects on terminal mesenteric larger than or equal to carotid greater than aorta). The terminal mesenteric and carotid arteries may accumulate and bind 45Ca at superficial membrane sites (readily exchangeable 45Ca) to a greater degree than does the aorta. If Ca++ located at these membrane sites contributes directly to the maintenance of mechanical responsiveness, then agents which alter membrane binding of Ca++ (e.g. neomycin) may exert a stronger action on these highly reactive vessels. Thus, contractile responsiveness in peripheral arteries may depend upon depots of superficially bound Ca++ to a greater degree than in the more centrally located aorta.

Effects of added or substituted potassium ion on 45 Ca movements in rabbit aortic smooth muscle

The effects of elevated potassium ion (K + ) concentration on radioactive calcium ( 45 Ca) movements and distribution were investigated in media-intimal strips prepared from rabbit aortic smooth muscle. 45 Ca uptake was measured in either normal (1.5 mM Ca 2+ ) or low-Ca (0.1 mM Ca 2+ ) solutions. In low-Ca solutions, elevating the K + concentration either by substituting equimolar (165.4 mM) K + for sodium (Na + ) (substituted-K solution) or by increasing K + concentration to 80 mM (added-K solution) increased the 45 Ca uptake. Exposure of the muscle strips to high K + concentrations during washout of 45 Ca decreased the 45 Ca efflux into either zero-Ca or low-Ca bathing solutions. Moreover, increased K + concentration elicited its effects in the presence or the absence of Na + . The decrease in 45 Ca efflux induced by substituted-K solution was also obtained in the presence of ethylenediaminetetraacetic acid (EDTA), but prior incubation of muscles with 1.5 mM strontium (Sr 2+ ) plus 45 Ca prevented this decrease in 45 Ca efflux. It would appear that the 45 Ca affected by high K + concentrations is at Sr-sensitive sites which are inaccessible to EDTA. If 45 Ca at these sites contributes directly to 45 Ca efflux, a shift of some of this 45 Ca to less superficial cellular sites might be responsible for the decreased efflux of 45 Ca observed in the presence of increased K + concentration.