QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

This Article Summary Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Sasaki, K. Articles by Furukawa, Y. Search for Related Content PubMed PubMed Citation Articles by Sasaki, K. Articles by Furukawa, Y.

The enterins inhibit the contractile activity of the anterior aorta of Aplysia kurodai

Kosei Sasaki¹, Yuko Fujisawa², Fumihiro Morishita¹, Osamu Matsushima¹ and Yasuo Furukawa^1,*

¹ Graduate School of Science, Department of Biological Science, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima 739-8526, Japan
² Suntory Institute Bioorganic Research, Shimamoto, Mishima, Osaka 618-8503, Japan

View larger version (102K): [in a new window]   Fig. 1. The enterin-immunopositive fibers and varicosities in the proximal region of the anterior aorta. The upper middle region in A is shown at higher magnification in B. Scale bars, 100 µm (A); 50 µm (B).

View larger version (7K): [in a new window]   Fig. 2. Effect of the enterin on the basal tonus of the anterior aorta. Sequential application of increasing concentrations of ENpa (mmol l-1) induced a concentration-dependent relaxation of the anterior aorta. After washing out ENpa, the muscle tonus was recovered gradually.

View larger version (22K): [in a new window]   Fig. 3. The enterins inhibit the NdWFamide-evoked tonic contraction of the anterior aorta. (Ai) The NdWFamide evoked contraction. 10-7 mol l-1 NdWFamide was applied for 8 min as indicated, before washing out. (Aii) Effect of 10-7 mol l-1 ENk on the NdWFamide-evoked contraction. 10-7 mol l-1 ENk was co-applied with NdWFamide 5 min after the initial NdWFamide application. (Aiii) Effect of 10-5 mol l-1 ENk on the NdWFamide-evoked contraction. (B) The concentration—response relationships of the enterins. The effects of six enterins (ENa, ENe, ENk, ENl, ENpa, ENr) on the NdWFamide-evoked contraction were tested. Amplitude of the contraction at the end of the application of the enterin (b in inset) was normalized to the one just before the application of the enterin (a in inset). Values are means ± S.E.M. (N=3-5) plotted against concentration of enterins. Smooth lines are best-fits of the equation described in Materials and methods. r2 and n were fixed to 100 and -1, respectively. r1 and logx0 for each fitting were as follows, respectively: ENa, 50.7, -6.9; ENe, 30.8, -6.8; ENk, 28.1, -7.0; ENl, 45.7, -6.8; ENpa, 26.0, -7.2; ENr, 43.5, -6.8.

View larger version (10K): [in a new window]   Fig. 4. The enterin inhibits the phasic contraction of the anterior aorta evoked by electrical stimulation of the vulvar nerve. (A) Effect of 10-8 moll-1 ENpa on the phasic contraction. To evoke a phasic contraction of the aorta, the vulvar nerve was stimulated by repetitive pulses (5V, 1 ms, 10 Hz) for 1 s. (B) The concentration—response of ENpa. The amplitude of the evoked contraction in the presence of ENpa was normalized to the one obtained before the application of the peptide. Values are means ± S.E.M. (N=4) plotted against the concentration of the peptide. The smooth line is a best-fit of the equation described in Materials and methods. r1, r2 and n were fixed to 0, 100 and -1, respectively. logx0 was estimated to be -8.1.

View larger version (16K): [in a new window]   Fig. 5. The enterins induce a hyperpolarization of the arterial muscle fibers. (A) Effect of ENpa on the membrane potential of the muscle fiber. ENpa was applied for 2 min at the concentrations indicated. (B) The concentration—response relationships of two enterins. Values are means ± S.E.M. (N=4-9) of the hyperpolarization plotted against the concentrations of enterins. The smooth lines are best-fits of the equation described in Materials and methods. r1 and n were fixed to 0 and 1, respectively. r2 and logx0 for each fitting were as follows, respectively: ENe, 13.2, -6.6; ENpa, 12.5, -7.0.

View larger version (17K): [in a new window]   Fig. 6. The enterin-induced hyperpolarization of the muscle is dependent on the external [K+], but not on the [Cl-]. (A) Effect of 10% K+-ASW on the ENpa-induced hyperpolarization. The traces show examples of the response. Histograms show means ± S.E.M. (N=3). (B) Effect of 50% Cl--ASW on the ENpa-induced hyperpolarization. Histograms show means ± S.E.M. (N=3). **P<0.01 (t-test).

View larger version (12K): [in a new window]   Fig. 7. 4-AP blocks the enterin-induced hyperpolarization. (A) Effect of 10-5 moll-1 4-AP on the 10-6 moll-1 ENpa-induced hyperpolarization of the muscle. (B) The concentration—response relationship of the 4-AP block. Amplitude of the ENpa-induced hyperpolarization in the presence of 4-AP was normalized to that seen in the absence of 4-AP. Values are means ± S.E.M. (N=3-5) of the ENpa-induced hyperpolarization plotted against [4-AP].

View larger version (10K): [in a new window]   Fig. 8. 4-AP blocks the inhibitory action of the enterin on the phasic contraction of the anterior aorta. (A) The action of 10-6 mol l-1 ENpa on the phasic contraction in the absence (Ai) or presence (Aii) of 1 mmol l-1 4-AP. The phasic contraction of the aorta was evoked by four repetitive stimuli (2 V, 1 ms, 10 Hz) of the vulvar nerve. (B) The inhibition of the nerve-evoked contraction by ENpa in the absence [4-AP(-)] or the presence [4-AP(+)] of 1 mmol l-1 4-AP. Histograms show means ± S.E.M. (N=4) of the relative amplitude of the contraction in the presence of ENpa.

View larger version (12K): [in a new window]   Fig. 9. 4-AP does not affect the inhibitory action of the enterin on the NdWFamide-evoked contraction of the anterior aorta. (A) Relaxation of the NdWFamide-induced contraction by ENpa in the absence (Ai) or presence (Aii) of 1 mmol l-1 4-AP. The aorta was contracted by 10-7 mol l-1 NdWFamide, and the action of 10-6 mol l-1 ENpa was tested. (B) The inhibition of the NdWFamide-induced contraction by ENpa in the absence [4-AP(-)] or the presence [4-AP(+)] of 1 mmol l-1 4-AP. Histograms show means ± S.E.M. (N=4) of the normalized NdWFamide-induced contraction in the presence of ENpa.