Biomedical subjects

H Kanaide

Publications and source records attributed to H Kanaide.

At least 73 records · Page 4Linked to original sources

PubMed1996

Expression of rho A and rho kinase mRNAs in porcine vascular smooth muscle.

It has recently been indicated that rho A and rho kinase may be involved in the mechanism for the increase in Ca2+ sensitivity in smooth muscle myofilaments. In the present study, we investigated the mRNA expression of rho A and rho kinase in porcine vascular smooth muscle cells (aorta, coronary artery, pulmonary artery, and pulmonary vein). In reverse transcription-polymerase chain reaction (RT-PCR) experiments, using total RNA from these tissue specimens and the primers designed in the conserved regions of each mRNA in human and bovine, rho A and rho kinase mRNAs were detected in all of these smooth muscle cells. An analysis of these PCR products by direct sequencing indicated that they were derived from each mRNA. The finding that both rho A and rho kinase mRNAs were expressed in the various porcine vascular smooth muscle cells strongly supports the idea that these proteins are involved in the mechanism dealing with the increase in Ca2+ sensitivity in the myofilaments of vascular smooth muscle cells.

Amino Acid Sequence↗

PubMed1996

Expression of calponin mRNA in porcine aortic endothelial cells.

Using reverse transcription polymerase chain reaction (RT-PCR), we determined the expression of the mRNAs for basic calponin isoforms, namely h1 and h2 forms, in the porcine aortic endothelial cells (PAECs) and aortic smooth muscle cells (PASMCs). The mRNAs for both h1 and h2 calponin isoforms were expressed in PAECs as well as in PASMCs. However, the expression of h2 isoform mRNA was more abundant than h1 isoform in PAECs, while h1 isoform was more abundant than h2 in PASMCs. These findings indicated the existence of calponin mRNA and the predominance of h2 over h1 calponin isoform in PAECs. It is suggested that h2 as well as h1, calponin isoform might have a physiological role in vascular endothelial cell. This is the first report which describes the existence of calponin h2-dominant cells.

Animals↗

PubMed1996

P2U purinergic activation leads to the cell cycle progression from the G1 to the S and M phases but not from the G0 to G1 phase in vascular smooth muscle cells in primary culture.

The regulation of the cell cycle by extracellular UTP was investigated in rat aortic smooth muscle cells in primary culture (VSMCs) by means of an immunocytochemical analysis of cell cycle-specific nuclear antigens. UTP induced a rise in the cytosolic Ca2+ concentration ([Ca2+]i) of VSMCs, which was desensitized by pretreatment with ATP, but not with 2-methylthioATP nor alpha, beta-methyleneATP. The incubation of serum-deprived G0 cells with platelet derived growth factor (PDGF) induced cell cycle progression into the G1 phase without any further progression into the S and M phases, while none of the nucleotides had any effect on the cell cycle of the G0 cells. The incubation of the PDGF-pretreated cells at the G1 phase with 2-methylthioATP or alpha, beta-methyleneATP had no effect on the cell cycle of G1 cells, while the incubation of the G1 cells with UTP, ATP, and ATP gamma S stimulated cell cycle progression into the S and M phases. These results thus indicate that P2U purinergic activation mediates a [Ca2+]i transient and a progression growth factor effect of nucleotides in VSMCs.

Adenosine Triphosphate↗

PubMed1996

P2U receptor is linked to cytosolic Ca2+ transient and release of vasorelaxing factor in bovine endothelial cells in situ.

1. With the use of front-surface fluorimetry and fura-2-loaded strips of bovine aortic valve, we characterized the [Ca2+]i transients induced in endothelial cells in situ using a non-selective purinergic agonist (adenosine 5'-triphosphate (ATP)), and selective agonists for P2X (alpha, beta-methylene ATP), P2Y (2-methylthio-ATP (2MeSATP)) and P2U (uridine 5'-triphosphate (UTP)) purinoceptors and an unrelated agonist bradykinin (BK). 2. Double staining with fura-2 and acetylated low-density lipoprotein labelled with 1,1'-dioctadecyl-3,3,3',3'-tetramethyl-indo-carbocyanine perchlorate showed that the fura-2 fluorescence arose exclusively from a single monolayer of endothelial cells covering the surface of the valvular strips. 3. All nucleotides (ATP, UTP and 2MeSATP) induced an elevation of the intracellular Ca2+ concentration ([Ca2+]i), with an initial transient peak and a subsequent lower sustained elevation. Blockade of the Ca2+ influx with 1 mM Ni2+ did not affect the peak levels of the [Ca2+]i transients, whereas it abolished the sustained increases in [Ca2+]i induced by these nucleotides. 4. The potency order of these nucleotides was 2MeSATP > ATP > UTP, while the order of the maximum responses was UTP = ATP > 2MeSATP. alpha, beta-Methylene ATP (up to 1 mM) had only a minimal effect. 5. Prolonged exposure to ATP or UTP, at concentrations giving a maximum response, desensitized the responses to ATP, UTP and 2MeSATP, but not to BK. Prolonged exposure to 2MeSATP at concentrations giving a maximum response did not desensitize the responses to UTP or BK, but did desensitize those to ATP and 2MeSATP. Prolonged exposure to BK did not induce heterologous desensitization to any of the three nucleotides. 6. [Ca2+]i elevation in valvular endothelial cells induced by UTP was associated with the relaxation of adjacent vascular medial strips precontracted with U-46619, the stable analogue of thromboxane A2. 7. We conclude that: (1) the peak elevation of the [Ca2+]i transient induced by these nucleotides is independent of extracellular Ca2+, which therefore suggests the release of intracellular Ca2+ and, (2) mature endothelial cells in situ, in a valvular preparation, have a common receptor for ATP and UTP (nucleotide or P2U receptor), which coexists with the P2Y receptor. Thus we propose that the activation of the nucleotide receptor, P2U, induces [Ca2+]i elevation in endothelial cells in situ, and thus leads to the release of vasorelaxing factors.

Adenosine Triphosphate↗

PubMed1996

Endothelin-1 and angiotensin II act as progression but not competence growth factors in vascular smooth muscle cells.

The direct effects of endothelin-1 and angiotensin II on cell cycle progression were investigated in rat aorta smooth muscle cells in primary culture. The phase of the cell cycle was determined by an immunocytochemical analysis of cell cycle-specific nuclear antigens. The primary cultured cells were synchronized in the G0 phase (100%) by serum deprivation for 24 h. Endothelin-1 (0.1 microM) or angiotensin II (1 microM) had no effect on the cell cycle of G0 cells, whereas platelet-derived growth factor (PDGF) stimulated the entry of the G0 cells into the G1 phase (100%) without a further progression to the S and M phases. Endothelin-1 or angiotensin II stimulated the progression of the PDGF-pretreated G1 cells to the S and M phases. Fura-2 microfluorometry revealed that, between the G0 and G1 cells, there were no differences in the extent and time course of cytosolic Ca2+ elevations induced by endothelin-1 or angiotensin II, which suggested that endothelin-1 and angiotensin II receptors and their signaling pathways regulating cytosolic Ca2+ remained intact in these cell phases. We thus conclude that endothelin-1 and angiotensin II require the prior G0/G1 transition induced by a competence growth factor such as PDGF to exert their mitogenic effects. These results suggest the important role of endothelin-1 and angiotensin II in atherosclerosis as promoters (progression growth factors), but not as initiators.

Angiotensin II↗

PubMed1996

Endothelin regulation of vascular tonus.

1. Following the identification of endothelin-1 (ET-1) in 1988, an increasing body of work has accumulated on this endothelium-derived vasoconstrictor peptide. 2. ET-1 may regulate the regional vascular tonus. 3. ET-1 may directly act on the underlying smooth muscle to increase the force in a paracrine manner. ET-1 may also act on the endothelium to release relaxing factors in an autocrine manner. In either case, both ETA and ETB receptors may be involved.

Animals↗

PubMed1996

Direct inhibitory effect of chlorpromazine on smooth muscle of the porcine pulmonary artery.

BACKGROUND: Chlorpromazine has been widely used by anesthesiologists to take advantage of its anesthesia-potentiating and vasorelaxing actions. However, the mechanisms of vasorelaxation induced by chlorpromazine are still not fully understood. METHODS: Using front-surface fluorometry of fura-2 and porcine pulmonary arterial strips, we investigated the effects of chlorpromazine on the intracellular Ca2+ concentration ([Ca2+]i) and force of vascular smooth muscle. The affinities of chlorpromazine and other neuroleptics to vascular alpha(1)-adrenergic receptors were then determined by a radio-ligand binding study. RESULTS: Chlorpromazine (as much as 1 microM) inhibited both the elevation of [Ca2+]i and force in pulmonary arterial smooth muscle induced by 80 mM K+-depolarization and 1 microM norepinephrine in a concentration-dependent manner. The extent of inhibition by chlorpromazine in norepinephrine-induced contraction was much greater than that in 80 mM K+-induced contraction. In contrast, as much as 1 microM chlorpromazine had no effect on the increases in [Ca2+]i or force induced by U46619, a thromboxane A2 analogue. Chlorpromazine also had no effect on the intracellular Ca2+ release induced by U46619. In a radio-ligand displacement study, chlorpromazine, haloperidol, phentolamine, trifluoperazine, and imipramine inhibited the specific binding of [3H]prazosin to the porcine aortic membranes, in this order of potency. CONCLUSIONS: Chlorpromazine induces vasorelaxation through an alpha-adrenergic blocking action as well as a calcium antagonistic action; the former action may, therefore, play a major role in chlorpromazine-induced vasorelaxation.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed1996

Some effects of nipradilol, a beta-antagonist possessing a nitroxy group, on smooth muscle of the pig coronary artery.

1. The effects of nipradilol, a beta-adrenoceptor antagonist which possesses a nitroxy group, on cytosolic Ca2+ concentration ([Ca2+]i), and on tension development were simultaneously measured by front-surface fluorometry and fura-2-loaded strips in the proximal portion of pig coronary arteries. 2. Nipradilol reduced in a concentration-dependent manner both the [Ca2+]i and tension, irrespective of whether the strips were unstimulated or exposed to either high K+ or histamine containing solutions. However, both in the case of contractions induced by high K+-depolarization and histamine stimulation, for a given [Ca2+]i elevation the tension which developed in the presence of nipradilol was smaller than that generated in its absence, so that the [Ca2+]i-tension curves during the contraction were shifted to the right. 3. In the absence of extracellular Ca2+, the [Ca2+]i elevation due to the release of Ca2+ from histamine-sensitive store was inhibited by nipradilol. Nipradilol had no effect on the [Ca2+]i elevation due to the release of Ca2+ from caffeine-sensitive stores; however, it did inhibit the caffeine-induced increase in tension. A derivative of nipradilol, which lacked a nitroxy molecule (Nip(-N)), had no effect on the [Ca2+]i and tension elevated by histamine or caffeine in the absence of extracellular Ca2+. 4. The beta-adrenoceptor agonist, isoprenaline, reduced [Ca2+]i tension when applied to steady state contractions induced by high K+, or at the peak level of tension to histamine. The reduction of [Ca2+]i and tension induced by isoprenaline was inhibited by Nip(-N) in a concentration-dependent manner and nipradilol inhibited the isoprenaline-induced relaxation with bell-shaped concentration-response curves. At lower concentrations, nipradilol acted as a beta-blocker, the IC50- value being smaller than that of Nip(-N), and at higher concentrations, it acted as a nitrovasodilator. 5. Thus, it is suggested that, at lower concentrations, nipradilol, an antianginal drug, acts as a beta-adrenoceptor antagonist. At higher concentrations, it relaxes the proximal portion of the coronary artery by directly reducing [Ca2+]i and the Ca2+-sensitivity of the myofilaments, apparently due to the presence of the nitroxy molecule.

Adrenergic beta-Agonists↗

PubMed1996

The mechanism of relaxation induced by atrial natriuretic peptide in the porcine renal artery.

1. The mechanisms underlying the relaxation of the porcine renal artery induced by atrial natriuretic peptide (ANP) were investigated, using front-surface fluorimetry with fura-2 and receptor-coupled permeabilization by alpha-toxin. 2. ANP decreased the cytosolic Ca2+ concentration ([Ca2+]i) and tension during the contraction induced by a high external K+ solution, in a concentration-dependent manner. This ANP-induced decrease in [Ca2+]i during the contraction induced by high K+ solution was composed of two phases, an initial rapid phase, followed by a maintenance phase. The initial rapid decrease in [Ca2+]i, but not the maintained decrease in [Ca2+]i, was inhibited when the tissue was treated with thapsigargin, a selective Ca2+ pump inhibitor of the sarcoplasmic reticulum. When the tissues were treated with thapsigargin and external Ca2+ was replaced by Ba2+, which cannot be transported by the Ca2+ pump, ANP did not induce a decrease in [Ba2+]i, even though the elevation of tension induced by Ba2+ was strongly inhibited. 3. In the absence of extracellular Ca2+, ANP inhibited the release of Ca2+ from the intracellular store induced by noradrenaline (NA). 4. The [Ca2+]i (abscissa scale)-tension (ordinate scale) relationship observed during the contraction induced by various concentrations of high external K+ solution was shifted downwards by the addition of 10(-8) M ANP, indicating that, at any given [Ca2+]i, the tension generated by high K+ solution was considerably inhibited by the addition of 10(-8) M ANP. The [Ca2+]i-tension curve of the contraction obtained by the cumulative application of external Ca2+ (0-3.75 mM) during depolarization with 118 mM K+ solution was shifted to the left by 3 x 10(-7) M NA. This NA-induced [Ca2+]i-tension relationship was shifted to the right by 10(-8) M ANP, indicating that the ANP-induced reduction of Ca(2+)-sensitivity operates during the contraction induced by NA. 5. In alpha-toxin-permeabilized preparations, ANP induced relaxation of tissues precontracted with a mixture of 3 x 10(-7) M Ca2+, 10(-5) M guanosine 5'-triphosphate (GTP) and 10(-6) M NA. Thus a component of ANP-induced relaxation took place by way of a reduction in the Ca2+ sensitivity of the myofilaments, independent of changes in [Ca2+]i. 6. These results indicate that ANP induces relaxation of the porcine renal artery by: (1) reducing [Ca2+]i mainly via the activation of the Ca2+ pumps located on the sarcoplasmic reticulum and sarcolemma, as well as via inhibition of agoinist-induced release of Ca2+ from the intracellular store; and (2) decreasing the Ca(2+)-sensitivity of the contractile elements.

Animals↗

PubMed1996

Dual regulation of cerebrovascular tone by UTP: P2U receptor-mediated contraction and endothelium-dependent relaxation.

1. The mechanisms of vascular tone regulation by extracellular uridine 5'-triphosphate (UTP) were investigated in bovine middle cerebral arterial strips. Changes in cytosolic Ca2+ concentration ([Ca2+]i) and force were simultaneously monitored by use of front-surface fluorometry of fura-2. 2. In the arterial strips without endothelium, UTP (0.1 microM-1 mM) induced contraction in a concentration-dependent manner. However, when the endothelium was kept intact, cumulative application of UTP (0.1-100 microM) (and only at 1 mM) induced a modest phasic contraction in arterial strips. This endothelium-dependent reduction of the UTP-induced contraction was abolished by 100 microM N omega-nitro-L-arginine (L-NOARG) but not by 10 microM indomethacin. In the presence of intact endothelium, UTP (30 microM) induced a transient relaxation of the strips precontracted with 30 nM U-46619 (a stable analogue of thromboxane A2), which was completely inhibited by pretreatment with L-NOARG but not with indomethacin. 3. In the endothelium-denuded strips, the contractile response to UTP was abolished by desensitization to either ATP gamma S or ATP (P2U receptor agonists), but not by desensitization to alpha, beta-methylene-ATP (P2x receptor agonist) or to 2-methylthio-ATP (P2Y receptor agonist). Desensitization to UTP abolished the contractile response to ATP. 4. In the endothelium-denuded artery, a single dose application of UTP induced an initial transient, and subsequently lower but sustained increase in [Ca2+]i and force. In the absence of extracellular Ca2+, UTP induced only the initial transient increases in [Ca2+]i and force, while the sustained increases in [Ca2+]i and force were abolished. UTP (1 mM) had no effect on the basic [Ca2+]i-force relationship obtained on cumulative application of extracellular Ca2+ at steady state of 118 mM K(+)-depolarization-induced contraction. 5. We conclude that in the presence of an intact endothelium, UTP-induced relaxation of preconstricted middle cerebral artery is mainly mediated indirectly, by the production of an endothelium-derived relaxing factor, but at high doses of UTP, vascular smooth muscle contraction is mediated directly via activation of P2U purinoceptor and [Ca2+]i elevation without Ca(2+)-sensitization of the contractile apparatus. UTP may thus exert a dual regulatory effect upon cerebrovascular tone, but in cases where the endothelium is impaired, it may also act as a significant vasoconstrictor.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed1996

CPA induces a sustained increase in [Ca2+]i of endothelial cells in situ and relaxes porcine coronary artery.

Using fura 2 fluorometry, we investigated the effect of cyclopiazonic acid (CPA), an inhibitor of Ca2+ pump adenosinetriphosphatase of the endoplasmic reticulum, on cystosolic Ca2+ concentration ([Ca2+]i) and tension in porcine aortic valvular endothelial cells and coronary arterial strips with endothelium. In normal physiological salt solution, CPA induced a sustained increase in [Ca2+]i in the valvular strips, whereas in Ca(2+)-free physiological salt solution, CPA elicited a transient elevation of [Ca2+]i. CPA(30 microM) relaxed coronary strips with endothelium precontracted by 100 nM U-46619; this relaxation was partially inhibited by N omega-nitro-L-arginine (100 microM). These results indicate that the CPA-induced increase in [Ca2+]i depends on the Ca2+ release and the Ca2+ influx in the endothelial cells in situ and that the CPA-induced endothelium-dependent decreases in [Ca2+]i and tension in the smooth muscle are due to the combined effect of N omega-nitro-L-arginine-sensitive and -resistant factors.

Animals↗

PubMed1996

Cell cycle--dependent expression of L- and T-type Ca2+ currents in rat aortic smooth muscle cells in primary culture.

The expression of L- and T-type Ca2+ channels has been reported to change during various biological events, including cellular differentiation and proliferation. The present study aimed to examine whether or not the expression of L- and T-type Ca2+ channels depends on the cell cycle in rat aortic smooth muscle cells in primary culture. Both the phase of the cell cycle and the functional expression of Ca2+ channels were determined in the same single cell, using an immunocytochemical analysis of cell cycle-specific nuclear antigens and a whole-cell voltage-clamp method, respectively. In the G0 (n = 130) and M (n = 75) phases, all cells showed only L-type Ca2+ currents. The cells showing a T-type Ca2+ current appeared in the G1 phase (37%, n = 85) and increased in the S phase (90%, n = 21). For L-type Ca2+ channels, the current density was significantly greater in the G1 phase than in the G0 and M phases. However, either the voltage-dependent properties or the dose-response relationships of Bay K 8644- and second messenger-induced modulations of L-type Ca2+ current did not differ in the four phases of the cell cycle. These findings thus indicate that the expression of L- and T-type Ca2+ channels depends on the cell cycle, whereas the characteristics of L-type Ca2+ channels do not differ between the phases of the cell cycle.

Animals↗

PubMed1996

The effects of calcitonin gene-related peptide on the cytosolic calcium concentration and force in the porcine coronary artery.

Using front-surface fluorometry and fura-2-loaded medial strips of the porcine coronary artery, we simultaneously monitored the cytosolic Ca++ concentration ([Ca++]i) and force development to investigate the mechanisms of vasorelaxation induced by calcitonin gene-related peptide (CGRP). CGRP actively decreased [Ca++]i of the strips at rest both in the presence and in the absence of extracellular Ca++. In the presence of extracellular Ca++, CGRP inhibited concentration-dependently the steady-state elevations of [Ca++]i and force induced by high-K+ depolarization and by histamine (HIS). The extent of the inhibition of force was much greater than the extent of reductions of [Ca++]i would lead one to expect. The [Ca++]i (abscissa)-force (ordinate) relationship at the peak levels of force during HIS-induced contractions shifted to the left of that observed with high-K+ depolarization. The [Ca++]i-force relationships of the contractions induced by high-K+ depolarization and by HIS shifted to the right as a result of the treatment with CGRP. In the absence of extracellular Ca++, CGRP inhibited the transient elevations of [Ca++]i induced by HIS but not by caffeine. Our results suggest that CGRP relaxes the porcine coronary artery by the following mechanisms: 1) the inhibition of Ca++ influx stimulated by HIS and by high-K+ depolarization, 2) the reduction of HIS-induced release of intracellular Ca++, without affecting a caffeine-sensitive mechanism, 3) an active decrease in the resting levels of [Ca++]i and 4) a decrease in the Ca(++)-sensitivity of the contractile apparatus.

Animals↗

PubMed1996

Differential effects of diltiazem and nitroglycerin on cytosolic Ca2+ concentration and on force in the bovine ophthalmic artery.

PURPOSE: To determine the mechanisms of inhibition by diltiazem (Dil) and nitroglycerin (NG) of the contraction induced by serotonin (5-HT) in the ophthalmic artery. METHODS: Using front-surface fluorometry of fura-2 and the medial strips of the bovine ophthalmic artery, [Ca2+]i and force were monitored simultaneously. Changes in the force at a constant [Ca2+]i were determined by use of receptor-coupled membrane permeabilization with alpha-toxin. RESULTS: In the presence of extracellular Ca2+, 5-HT (10(-5) M) induced an initial transient and subsequently lower steady state elevation of [Ca2+]i. The transient elevation of [Ca2+]i was dependent on both intracellular and extracellular [Ca2+]i, whereas the steady state elevation was dependent on only extracellular Ca2+. For a given level of elevation of [Ca2+]i, 5-HT produced a greater force than the depolarization with high external K+ (118 mM) solution. In the permeabilized ophthalmic artery smooth muscle, 5-HT enhanced the contractile response to constant cytosolic Ca2+ (pCa 6.5) in the presence of guanosine triphosphate (GTP, 10 microM), but not in its absence. Therefore, 5-HT induces [Ca2+]i elevation, depending on both extracellular (Ca2+ influx) and intracellular Ca2+ (Ca2+ release), and it potentiates the Ca2+ sensitivity of the contractile apparatus through the activation of G-proteins. 5-HT-induced release of Ca2+ from the store was inhibited by NG, but not by Dil, in a concentration-dependent manner. However, neither NG nor Dil inhibited caffeine (20 mM)-induced release of Ca2+ from the store. Dil (10 microM) and NG (10 microM) inhibited in a concentration-dependent manner the steady state elevations of [Ca2+]i (Ca2+ influx) and force induced by 5-HT (10 microM) in the presence of extracellular Ca2+. Dil equally inhibited the steady state elevations of [Ca2+]i and force induced by 5-HT, whereas NG inhibited the force to a greater extent than expected from the reduction in [Ca2+]i. In the permeabilized ophthalmic artery smooth muscle, NG (10 microM), but not Dil (10 microM), decreased the force development induced by GTP (10 microM) and 5-HT (10 microM) at constant [Ca2+]i (pCa 6.5). These results indicate that NG, but not Dil, decreases the Ca2+ sensitivity of contractile apparatus. CONCLUSIONS: The authors found that 5-HT contracts the ophthalmic artery smooth muscle by the elevation of [Ca2+]i mediated by the release of intracellular Ca2+ and the influx of extracellular Ca2+, as well as by an increase in the Ca2+ sensitivity of the contractile apparatus through the activation of G-proteins, and that Dil relaxes 5-HT-mediated contraction of ophthalmic artery primarily by inhibiting the Ca2+ influx and, hence, by decreasing [Ca2+]i without having any effect on the Ca2+ sensitivity of the contractile apparatus. Nitroglycerin relaxes the ophthalmic artery not only by decreasing [Ca2+]i (inhibition of both the Ca2+ release and Ca2+ influx) but also by decreasing the Ca2+ sensitivity of the contractile apparatus.

Animals↗

PubMed1995

Autocrine regulation of the renal arterial tone by adrenomedullin.

We tested the hypothesis that adrenomedullin (ADM), a recently isolated hypotensive peptide, is an autocrine transmitter in renal arterial smooth muscle cells (RASMCs). Fura-2 fluorometry revealed that ADM decreases both the cytosolic Ca2+ concentration ([Ca2+]i) and tension induced by 0.3 microM phenylephrine (PE) in porcine RASMCs. The expression of ADM mRNA in RASMCs was assessed by the reverse transcription polymerase chain reaction (RT-PCR), using the total RNA from the RASMCs and the specific primers for the porcine ADM mRNA. A band with an expected size could be detected only when the reverse transcriptase was added, thus indicating that the porcine RASMCs express ADM mRNA. These results therefore suggested that ADM plays an important role in the regulation of the renal vascular tone, not only as a circulating hormone, but also as an autocrine transmitter.

Adrenomedullin↗

PubMed1995

Adrenomedullin decreases both cytosolic Ca2+ concentration and Ca(2+)-sensitivity in pig coronary arterial smooth muscle.

Adrenomedullin (AM) is a newly identified vasorelaxant peptide which circulates in human plasma. We investigated the cellular mechanisms of AM-induced relaxation in the pig coronary artery, using fura-2 fluorometry and receptor-coupled membrane permeabilization by alpha-toxin. AM inhibited both the elevations of cytosolic Ca2+ concentration ([Ca2+]i) and the tension induced by high K(+)-depolarization and by U46619. The extent of the tension inhibition was much greater than expected based on the extent of reductions of [Ca2+]i. Thus, the [Ca2+]i (abscissa)-tension (ordinate) relation shifted to the right by AM. In alpha-toxin-permeabilized strips, AM decreased the tension development at constant [Ca2+]i (pCA 6.5) in the presence of GTP, whereas GDP beta S antagonized this effect. We thus conclude that AM relaxes the coronary artery not only by decreasing [Ca2]i but also by decreasing the Ca(2+)-sensitivity of the contractile apparatus, as mediated by G-protein.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed1995

High D-glucose stimulates the cell cycle from the G1 to the S and M phases, but has no competent effect on the G0 phase, in vascular smooth muscle cells.

The effects of high (28mM) D-glucose (HG) on the cell cycle progression were investigated in rat aorta vascular smooth muscle cells (VSMCs) in primary culture, using an immunocytochemical analysis of cell-cycle-specific nuclear antigens. HG had no effect on the cell cycle of the serum-deprived G0 cells, whereas platelet-derived growth factor (PDGF) stimulated the entry of the G0 cells to the G1 phase without a further progression to the S and M phases. HG, but neither mannitol nor L-glucose, stimulated the progression of the PDGF-pretreated G1 cells to the S and M phases, which was blocked by calphostin-C, a protein kinase C (PKC) blocker. HG did not affect the cytosolic Ca2+ concentration ([Ca2+]i). These data suggest that HG has no competent effect on the G0 cells and acts as a progression growth factor (to stimulate the cell cycle from the G1 to the S/M) in VSMCs through the mechanism, which may be insensitive to [Ca2+]i and mediated by PKC.

Animals↗

PubMed1995

Resting load regulates cytosolic calcium-force relationship of the contraction of bovine cerebrovascular smooth muscle.

1. We determined the effects of a change in preload, or resting load, on the development of force and on cytosolic calcium concentration ([Ca2+]i) during the contraction induced by high K+ depolarization and by the stable analogue of thromboxane A2, U-46619, using front-surface fluorometry and medial strips of bovine middle cerebral artery loaded with fura-2. 2. Increase in resting load of strips from 0.495 mN (low load; 0.85L(max)) to 1.98 mN (optimal load; L(max)) elevated resting levels of [Ca2+]i slightly, and, significantly, after a delay of a few seconds. The force developed by high K+ depolarization at resting load of 1.98 mN was much greater than that at a resting load of 0.495 mN (191.8% of that at 0.495 mN); however, there was no difference in [Ca2+]i elevation induced by high K+ depolarization between resting loads of 0.495 and 1.98 mN. 3. Both in the presence and absence of extracellular Ca2+, the force developed by U-46619 (0.1 microM) at resting load of 1.98 mN was also much greater than that at a resting load of 0.495 mN. Both in the presence and absence of extracellular Ca2+, there was no difference in the [Ca2+]i transients induced by U-46619 between two different resting loads. 4. The [Ca2+]i-force relationship during the contraction induced by high K+ depolarization was shifted to the left when the resting load was increased from 0.495 to 1.98 mN. At 0.495 mN resting load, this Ca(2+)-force relationship was shifted to the left by U-46619. This left-side shift of the curve by U-46619 was further enhanced by the increase in resting load from 0.495 to 1.98 mN. 5. The augmentation of force development induced by the change in resting load (from 0.495 to 1.98 mN) was not affected by a relatively specific inhibitor of protein kinase C, 1-(5-isoquinolinesulphonyl)-2-methylpiperazine dihydro-chloride (H-7; 10 microM). 6. We conclude that (1) at a given degree of [Ca2+]i elevation, the developed force induced by U-46619 was greater than that induced by high K+ depolarization, and (2) preload, or resting load (below optimal load), regulates contractile responsiveness of cerebrovascular smooth muscle to various stimulations, mainly by modulating the [Ca2+]i-force relationship, without affecting the extent of [Ca2+]i elevation. The results suggest the possibility that Ca(2+)-insensitive pathways may be involved in the stretch-dependent regulation of Ca2+ sensitivity of the contractile apparatus in smooth muscle.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗