• The Korean Journal of Physiology and Pharmacology
• /
• v.16 no.5
• /
• pp.297-303
• /
• 2012

This study was designed to elucidate high $K^+$-induced relaxation in the human gastric fundus. Circular smooth muscle from the human gastric fundus greater curvature showed stretch-dependent high $K^+$ (50 mM)-induced contractions. However, longitudinal smooth muscle produced stretch-dependent high $K^+$-induced relaxation. We investigated several relaxation mechanisms to understand the reason for the discrepancy. Protein kinase inhibitors such as KT 5823 (1 ${\mu}M$) and KT 5720 (1 ${\mu}M$) which block protein kinases (PKG and PKA) had no effect on high $K^+$-induced relaxation. $K^+$ channel blockers except 4-aminopyridine (4-AP), a voltage-dependent $K^+$ channel ($K_V$) blocker, did not affect high $K^+$ -induced relaxation. However, N(G)-nitro-L-arginine and 1H-(1,2,4)oxadiazolo (4,3-A)quinoxalin-1-one, an inhibitors of soluble guanylate cyclase (sGC) and 4-AP inhibited relaxation and reversed relaxation to contraction. High $K^+$-induced relaxation of the human gastric fundus was observed only in the longitudinal muscles from the greater curvature. These data suggest that the longitudinal muscle of the human gastric fundus greater curvature produced high $K^+$-induced relaxation that was activated by the nitric oxide/sGC pathway through a $K_V$ channel-dependent mechanism.

• The Korean Journal of Physiology and Pharmacology
• /
• v.15 no.6
• /
• pp.405-413
• /
• 2011

This study was designed to elucidate high-$K^+$ induced response of circular and longitudinal smooth muscle from human gastric corpus using isometric contraction. Contraction from circular and longitudinal muscle stripes of gastric corpus greater curvature and lesser curvature were compared. Circular smooth muscle from corpus greater curvature showed high $K^+$ (50 mM)-induced tonic contraction. On the contrary, however, longitudinal smooth muscle strips showed high $K^+$ (50 mM)-induced sustained relaxation. To find out the reason for the discrepancy we tested several relaxation mechanisms. Protein kinase blockers like KT5720, PKA inhibitor, and KT5823, PKG inhibitor, did not affect high $K^+$-induced relaxation. $K^+$ channel blockers like tetraethylammonium (TEA), apamin (APA), glibenclamide (Glib) and barium ($Ba^{2+}$) also had no effect. However, N(G)-nitro-L-arginine (L-NNA) and 1H-(1,2,4) oxadiazolo (4,3-A) quinoxalin-1-one (ODQ), an inhibitor of soluble guanylate cyclase (sGC) and 4-AP (4-aminopyridine), voltage-dependent $K^+$ channel (KV) blocker, inhibited high $K^+$ -induced relaxation, hence reversing to tonic contraction. High $K^+$-induced relaxation was observed in gastric corpus of human stomach, but only in the longitudinal muscles from greater curvature not lesser curvature. L-NNA, ODQ and KV channel blocker sensitive high $K^+$-induced relaxation in longitudinal muscle of higher portion of corpus was also observed. These results suggest that longitudinal smooth muscle from greater curvature of gastric corpus produced high $K^+$-induced relaxation which was activated by NO/sGC pathway and by $K_V$ channel dependent mechanism.

• The Korean Journal of Physiology
• /
• v.21 no.1
• /
• pp.47-58
• /
• 1987

It has been reported that the luteal function may be regulated by the intracellular $Ca^{++}$ level which may be adjusted partially by the high affinity $Ca^{++}-ATPase$ in luteal cell membranes. Then, one may expect that luteotropic and/or luteolytic agents, such as gonadotropins, prostaglandin $F_{2{\alpha}}\;(PGF_{2{\alpha}})$ and ouabain, affect the intracellular $Ca^{++}$ level. In this present study, therefore, we examined the effects of luteinizing hormone (LH, or human chorionic gonadotropin, hCG), $PGF_{2{\alpha}}$ and ouabain on the kinetic properties of the high affinity $Ca^{++}-ATPase$ in light membrane, heavy membrane, and microsomal fractions from the highly luteinized ovary. LH (or hCG) increased the affinity and the Vmax for $Ca^{++}$ both in light membrane and heavy membrane. $PGF_{2{\alpha}}$ increased the Vmax in light membrane and decreased the Km in heavy membrane for $Ca^{++}$ at low concentration $(5\;{\mu}g/ml)$. At higher concentration, however, $PGF_{2{\alpha}}$ oppositly affected on kinetic properties, that shown at low concentration. Ouabain, a potent inhibitor of $Na^+-K^+-ATPase$, increased the Km at high concentration $(10^{-4}\;M)$, however, decreased the Vmax for $Ca^{++}$ in light membrane at low concentration $(10^{-6}\;M)$. Also, ouabain increased the Km for $Ca^{++}$ in heavy membrane without changes in the Vmax at both concentrations. It seems that LH and low dose of $PGF_{2{\alpha}}$ increase the intracellular $Ca^{++}$ level and cause in activation of $Ca^{++}-ATPase$, however, higher dose of $PGF_{2{\alpha}}$ and ouabain inhibit directly $Ca^{++}-ATPase$ activity and result in increase in intracellular $Ca^{++}$ level. According to the above results, we suggest that luteotropic and/or luteolytic agents regulate the luteal progesterone $(P_4)$ production through two different pathways; one is cyclic adenosine monophosphate (cAMP)-dependent and another is $Ca^{++}-dependent$. Intracellula. $Ca^{++}$ level regulated by the high affinity $Ca^{++}-ATPase$ may affect both pathways in a time-dependent fashion. LH (or hCG) acts on the luteal $P_4$ production via both pathways. The initial step is $Ca^{++}$ dependent, and the late step is cAMP dependent. $PGF_{2{\alpha}}$ and ouabain increase the intracellular $Ca^{++}$ concentration so that basal luteal $P_4$ production is increased and LH-stimulated $P_4$ production is inhibited by the inhibiting LH-dependent adenylate cyclase activity.

• YAKHAK HOEJI
• /
• v.41 no.3
• /
• pp.389-398
• /
• 1997

Non-adenergic non-cholinergic (NANC) innervation on the circular muscle of the rabbit gastric body was investigated by observing the magnitudy of relaxations induced by the elec trical field stimulation (EFS). Strips were cut from the greater curvature of the gastric body and stimulated with 5s trains of 0.5 ms pulses at 1-20 Hz, 40 V. The EFS induced transient frequency-dependent contractons, followed by a slowly recovering relaxation ewpecially at higher frequency of the EFS. In the presence of atropine and guanethidine, the contractions were virtually abolished, while the frequency-dependent relaxations by the EFS remained unaffected. The magnitude of relaxations progressively decreased as the location of the strips gets closer to the bottom of the gastric body. The relaxations were ablished by tetrodotoxin, indicating that their orgin is the NANC nerve stimulation. NG-nitro-L-arginine (L-NNA, 10-$100{\mu}M$), the inhibitor of nitric oxide (NO)-synthase, caused a concentration-dependent inhibition of the NANC relaxations. The inhibitory effects of L-NNA were not affected gy the location of the strips and were reversed by L-arginine, the precursor of NO-biosynthesis. Hemoglobin (20-$60{\mu}M$), a NO scavenger, inhibited the NANC relaxation s in a concentration-dependent manner. This inhibition was more prominent in the NANC relaxations observed in the lower portion of the gastric body and the relaxations induced ly lower frequencies of the EFS. Methyelne blue (10-$100{\mu}M$), an inhibitor of cytosolic guanylate cyclase, markedly inhibited the NANC relaxations, almost abolishing the response at a higher dose ($100{\mu}M$). These results suggest that NANX innervation of the rabbit gastric body progeressively decrease as he location of the strips gets closer to the bottom of the gastric body, and that the NANC relaxation is primarily mediated by NO-guanosine 3',5'-cyclic monophophate (cyclic GMP).

• Biomedical Science Letters
• /
• v.13 no.3
• /
• pp.197-206
• /
• 2007

P2X receptors are membrane-bound ion channels that conduct $Na^+,\;K^+$, and $Ca^{2+}$ in response to ATP and its analogs. There are seven subunits identified so far ($P2X_1-P2X_7$). $P2X_2$ receptors are known to be expressed in a wide range of organs including brains and adrenal grands. PC12 cells are originated from adrenal grand and differentiated by nerve growth factor or pituitary adenylate cyclase activating poly peptide (PACAP). Previous studies indicate that $P2X_2$ receptor activation in PC12 cells couples to $Ca^{2+}-dependent$ release of catecholamine and ATP. It is known that acidic pH potentiates ATP currents at $P2X_2$ receptors. This leads to a hypothesis that $P2X_2$ receptors may play an important role in PC12 cell differentiation, one of the characteristics of which is neurite outgrowth, induced by the hormones under lower pH. In the present study, we isolated several clones which potentiate neurite outgrowth by PACAP in acidic pH (6.8), but not in alkaline pH (7.6). RT-PCR and electrophysiology data indicate that these clones express only functional $P2X_2$ receptors in the absence or presence of PACAP for 3 days. Potentiation of neurite outgrowth resulted from PACAP (100 nM) in acidic pH is inhibited by the two P2X receptor antagonists, suramin and PPADS ($100\;{\mu}M)$ each), and exogenous exprerssion of ATP-binding mutant $P2X_2$ receptor subunit ($P2X_2[K69A]$). However, acid sensing ion channels (ASICs) are not involved in PACAP-induced neurite outgrowth potentiation in lower pH since treatments of an inhibitor of ASICs, amyloride ($10\;{\mu}M$), did not give any effects to neurite extension. The vesicular proton pump ($H^+-ATPase$) inhibitor, bafilomycin (100 nM), reduced neurite extension indicating that ATP release resulted from $P2X_2$ receptor activation in PC12 cells is needed for neurite outgrowth. These were confirmed by activation of mitogen activated protein kinases, such as ERKs and p38. These results suggest roles of ATP and $P2X_2$ receptors in hormone-induced cell differentiation or neuronal synaptogenesis in local acidic environments.

• Herbal Formula Science
• /
• v.14 no.1
• /
• pp.105-119
• /
• 2006

Objectives & Methods : This present study was performed to investigate the effect of Hwadamtongrak-Tang extract (HTT) on the regulation of cerebral hemodynamics in terms of regional cerebral blood flow (rCBF) and mean arterial blood pressure (MABP)] in normal and cerebral ischemic rats. Also the effects of HTT on changes in local blood flow, inhibition of LD H activity in neuronal cells, and levels of cytokine production in the serum were determined in the ischemic rat model. The major findings are summarized below. Results : 1. HTT significantly increased rCBF in a dose-dependent manner, but MABP was not changed by HTT treatment. These results suggest that HTT may increase rCBF by dilating cerebral arterial diameter. 2. HTT-induced increase in rCBF was blocked by pretreatment with cyclooxygenase inhibitor indomethacin (IDN, 1 mg/kg, i.p.) and MABP was significantly increased by ID N. 3. Pretreatment of methylene blue $(MTB,\;10\;{\mu}g/kg,\;i.p.)$, an inhibitor of guanylate cyclase, significantly decreased both rCBP and MABP in HTT-treated rats. 4. HTT treatment significantly increased rCBP to a stable level during the period of cerebral reperfusion. 5. HTT significantly inhibited LD H activity in neuronal cells, suggesting a neuroprotection by HTT. 6. Serum interleukin $(IL)-1{\beta}$ and tumor necrosis factor $(TNF)-{\alpha}$ levels were significantly decreased in the femoral artery 1 hr after middle cerebral arterial occlusion in HTT-treated rats. IL-10 levels in the serum were significantly increased by HTT treatment whereas transforming growth factor $(TGF)-{\beta}$ levels were similar between HTT-treated and control groups. 7. Serum interleukin $(IL)-1{\beta}$ and tumor necrosis factor $(TNF)-{\alpha}$ levels were significantly decreased in the femoral artery 1 hr after reperfusion in HTT-treated rats. Serum IL-10 levels were significantly decreased in HTT-treated rats compared with the control group, and no significant changes in $(TGF)-{\beta}$ in the serum were observed by HTT treatment. Conclusions: The present data suggest that HTT may have an anti-ischemic effect via the improvement of cerebral hemodynamics and thus protect the brain from ischemic damage.

• The Journal of Korean Medicine
• /
• v.26 no.3 s.63
• /
• pp.188-203
• /
• 2005

Objectives : This study was designed to investigate the effects of Jayun-tang extract (JYT) on the change of cerebral hemodynamics [regional cerebral blood flow (rCBF), pial arterial diameter (PAD) and mean arterial blood pressure (MABP)] in normal and cerebral ischemic rats, na to determine the mechanisms of action of JYT. Methods : We investigated whether JYT inhibits lactate dehydrogenase activity in neuronal cells and cytokines production in serum of cerebral ischemic rats. Results : 1. JYT significantly increased rCBF and PAD in a dose-dependent manner, but MABP was not changed by injecting JYT. These results suggested JYT significantly increased rCBF by dilating PAD. 2. The JYT-induced increase in rCBF was significantly inhibited from pretreatment with indomethacin (1mg/kg, i.p.), an inhibitor of cyclooxygenase and methylene blue $(10{\mu}g/kg, i.p.)$, an inhibitor of guanylate cyclase. 3. The JYT-induced dilation in PAD was significantly inhibited from pretreatment with indomethacin, but was increased by pretreatment with methylene blue. 4 The JYT-induced increase in MABP was reduced by pretreatment with indomethacin and methylene blue. 5. JYT significantly inhibited lactate dehydrogenase activity in neuronal cells. These results suggest that JYT prevented the neuronal death. 6. Both rCBF and PAD were significantly and stably increased by JYT $(10{\mu}g/kg,\;i.p.)$ during the Period or cerebral reperfusion, which contrasted with the findings of rapid and marked increase in the control group. 7. In cytokine production in the serum drawn from femoral artery 1hr after middle cerebral artery occlusion, the sample group showed significantly decreased production of $IL-1\beta$ and $TNF-\alpha$ as well as increased production of IL-10 and $TGF-\beta$ compared with rho control group. 8. In cytokine production in the serum drawn from femoral artery 1hr after reperfusion, the sample group showed significantly decreased production of $IL-1\beta$ and $TNF-\alpha$ as well as significantly increased production of IL-10 and $TGF-\beta$ compared with the control group. Conclusions : JYT mediated by cyclooxygenase had an inhibitive effect on brain damage by inhibiting lactate dehydrogenase activity, $IL-1\beta$ and $TNF-\alpha$ production, and by accelerating IL-10 and $TGF-\beta$ production. The author feels that JYT had anti-ischemic effects through the improvement of cerebral hemodynamics and inhibitive effects on brain damage.

• Development and Reproduction
• /
• v.22 no.2
• /
• pp.143-153
• /
• 2018

The large extracellular domain of glycoprotein hormone receptors is a unique feature within the G protein-coupled receptors (GPCRs) family. After interaction with the hormone, the receptor becomes coupled to Gs, which, in turn stimulates adenylyl cyclase and the production of cAMP. Potential phosphorylation sites exist in the C-terminal region of GPCRs. The experiments described herein represent attempts to determine the functions of the eel follicle-stimulating hormone receptor (eelFSHR). We constructed a mutant of eelFSHR, in which the C-terminal cytoplasmic tail was truncated at residue 614 (eelFSHR-t614). The eelFSHR-t614 lacked all potential phosphorylation sites present in the C-terminal region of eelFSHR. In order to obtain the eelFSHR ligand, we produced recombinant follicle-stimulating hormone ($rec-eelFSH{\beta}/{\alpha}$) in the CHO-suspension cells. The expression level was 2-3 times higher than that of the transient expression of eelFSH in attached CHO-K1 cells. The molecular weight of the $rec-eelFSH{\beta}/{\alpha}$ protein was identified to be approximately 34 kDa. The cells expressing eelFSHR-t614 showed an increase in agonist-induced cAMP responsiveness. The maximal cAMP responses of cells expressing eelFSHR-t614 were lower than those of cells expressing eelFSHR-wild type (eelFSHR-WT). The $EC_{50}$ following C-terminal deletion in CHO-K1 cells was approximately 60.4% of that of eelFSHR-WT. The maximal response in eelFSHR-t614 cells was also drastically lower than that of eelFSHR-WT. We also found similar results in PathHunter Parental cells expressing ${\beta}$-arrestin. Thus, these data provide evidence that the truncation of the C-terminal cytoplasmic tail phosphorylation sites in the eelFSHR greatly decreased cAMP responsiveness and maximal response in both CHO-K1 cells and Path-Hunter Parental cells expressing ${\beta}$-arrestin.

• The Korean Journal of Physiology and Pharmacology
• /
• v.4 no.6
• /
• pp.471-477
• /
• 2000

In the rabbit renal artery, acetylcholine $(ACh,\;1\;nM{\sim}10\;{\mu}M)$ induced endothelium-dependent relaxation of arterial rings precontracted with norepinephrine $(NE,\;1\;{\mu}M)$ in a dose-dependent manner. $N^G-nitro- L-arginine$ (L-NAME, 0.1 mM), an inhibitor of NO synthase, or ODQ $(1\;{\mu}M),$ a soluble guanylate cyclase inhibitor, partially inhibited the ACh-induced endothelium-dependent relaxation. The ACh-induced relaxation was abolished in the presence of 25 mM KCl and L-NAME. The cytochrome P450 inhibitors, 7- ethoxyresorufin $(7-ER,\;10\;{\mu}M),$ miconazole $(10\;{\mu}M),$ or 17-octadecynoic acid $(17-ODYA,\;10\;{\mu}M),$ failed to inhibit the ACh-induced relaxation in the presence of L-NAME. 11,12-epoxyeicosatrienoic acid $(11,12-EET,\;10\;{\mu}M)$ had no relaxant effect. The ACh-induced relaxation observed in the presence of L-NAME was significantly reduced by a combination of iberiotoxin $(0.3\;{\mu}M)$ and apamin $(1\;{\mu}M),$ and almost completely blocked by 4-aminopyridine (5 mM). The ACh-induced relaxation was antagonized by $P_{2Y}$ receptor antagonist, cibacron blue $(10\;and\;100\;{\mu}M),$ in a dose-dependent manner. Furthermore, 2-methylthio-ATP (2MeSATP), a potent $P_{2Y}$ agonist, induced the endothelium-dependent relaxation, and this relaxation was markedly reduced by either the combination of iberiotoxin and apamin or by cibacron blue. In conclusion, in renal arteries isolated from rabbit, ACh produced non-NO relaxation that is mediated by an EDHF. The results also suggest that ACh may activate the release of ATP from endothelial cells, which in turn activates $P_{2Y}$ receptor on the endothelial cells. Activation of endothelial $P_{2Y}$ receptors induces a release of EDHF resulting in a vasorelaxation via a mechanism that involves activation of both the voltage-gated $K^+$ channels and the $Ca^{2+}-activated\;K^+\;channels$. The results further suggest that EDHF does not appear to be a cytochrome P450 metabolite.

• Journal of Plant Biotechnology
• /
• v.40 no.3
• /
• pp.125-134
• /
• 2013

Lipid droplets called plastoglobules are present in all plastid types. In chloroplasts, they are surrounded by the outer lipid monolayer from and connected to thylakoid membrane. The plastoglobule core contains the neutral lipids, which includes prenylquinones, triacylglycerols, and carotenoids. During stress and various developmental stages such as senescence, the size and number of plastoglobules increase due to the accumulation of lipids. Plastoglobules proteome revealed the presence of metabolic enzymes as well as structural proteins, plastoglobulins/fibrillins. Among the metabolic enzymes, the tocopherol cyclase, VTE1 and the NADPH quinine dehydrogenase, NDC1 have demonstrated that these participate in isoprenoid lipid metabolic pathways at the plastoglobule, notably in the metabolism of prenylquinones (tocopherol, plastoquinol and phylloquinone).