| 1. |
- Adner, Mikael
(författare)
-
Altered expression of contractile endothelin receptors in the vascular bed
- 1998
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis aims at characterizing the endothelin (ET) receptors in different vascular beds of man and rat. The ET-A receptor was shown to be the only contractile ET receptor present in all vascular regions, with the exception of the rat mesenteric vein where a weak ET-B receptor-mediated contraction was seen. Treatment with antisense oligodeoxynucleotides to the ET-A receptor mRNA during organ culture showed a decrease of the ET-1-induced contraction in the human temporal artery. However, in human omental arteries there was an increase in response to ET-B receptor agonists together with an increase of ET-B receptor mRNA following organ culture. This phenomenon suggests that contraction is due to upregulation of ET-B receptors. The level of expression of contractile ET-B receptors varies among different vascular regions following organ culture; it is most enhanced in small arteries and veins, whereas it is low or absent in large arteries. The upregulation seems to be most pronounced in the mesenteric region. The culture medium components do not induce upregulation of ET-B receptors, since there was no difference between addition of foetal calf serum or buffer solution. However, when the physiological conditions were altered, by the exclusion of energy supply (glucose) or during culture below normal temperature (at 4 °C), the upregulation was attenuated or totally blunted. This indicates that the phenomenon is a metabolically active process. Experiments with and without endothelium or tension did not alter the level of ET-B receptor expression. This suggests that there is no intrinsic mechanisms that keeps the ET-B receptors at low expression levels. ET-B receptors are shown to be upregulated in several vascular diseases. The use of organ culture can be a very useful tool to study both the function and the regulation of contractile ET-B receptors.
|
|
| 2. |
- Adner, Mikael, et al.
(författare)
-
Contractile endothelin-B (ETB) receptors in human small bronchi
- 1996
-
Ingår i: European Respiratory Journal. - : European Respiratory Society (ERS). - 1399-3003 .- 0903-1936. ; 9:2, s. 351-355
-
Tidskriftsartikel (refereegranskat)abstract
- Endothelins (ETs) are a family of novel regulatory peptides and various lines of evidence suggest an important role for ETs in regulating pulmonary function. Two receptors for endothelin, ETA and ETB, have been found in the human lung, and according to recent studies a non-ETA receptor seems to mediate the contraction of large sized human bronchi. Several studies have emphasized the importance of small bronchi in the pathogenesis of airway disease. In the present paper, improved methodology was used which enables in vitro studies of small human bronchi down to a diameter of 0.5-1.0 mm. Using the new methodology we have tried to further characterize this receptor. Small bronchi from the distal parts of the bronchial tree were obtained from pulmonary tissue removed from 15 patients with lung cancer. They were dissected and cut into ring segments, in which isometric tension was recorded. ET-1, ET-2 and ET-3 elicited strong concentration-dependent contractions of the human small bronchus. Basically, the three peptides were equipotent with about the same maximal response. Upon reapplication, they all showed the same tachyphylaxis pattern, reaching half the initial contraction. Comparative analysis of IRL 1620, a selective ETB receptor agonist, revealed that the effect of the ETB agonist was, in all respects, similar to the responses induced by the ETs. PD 145065, a combined ETA/ETB receptor antagonist competitively inhibited the contractions induced by IRL 1620, whereas FR139317, a selective ETA receptor antagonist, was without effect. In conclusion, the present study shows that accurate measurements can be made in vitro on small human bronchi and all present data are in favour of an ETB receptor mediating endothelin-induced contraction of human bronchi smaller than 1.0 mm.
|
|
| 3. |
- Adner, Mikael, et al.
(författare)
-
Regional variation in appearance of vascular contractile endothelin-B receptors following organ culture
- 1998
-
Ingår i: Cardiovascular Research. - 1755-3245. ; 37:1, s. 254-262
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: The aim of this study was to investigate the appearance of contractile endothelin (ET)-B receptors following organ culture in different vascular regions. METHOD: The contractile responses of vascular smooth muscle induced by ET-1 and the selective ETB receptor agonist sarafotoxin 6c (S6c) were investigated in circular segments representing eight vascular regions in the rat (aorta, femoral artery, mesenteric artery, branch of the mesenteric artery, proximal and distal parts of the caudal artery, femoral and mesenteric veins). To allow the ETB receptor to be expressed, the segments were placed in organ culture for 1 to 5 days. Pharmacological characterisation of the ET receptors was performed in mesenteric arterial segments. All contractile responses were measured in percentage of K(+)-induced contraction. RESULTS: ET-1 induced strong concentration-dependent contractions of all fresh (not cultured) segments. S6c had negligible effects on all fresh vessels with the exception of the mesenteric vein, where a small contraction was seen. After 1 day of organ culture all tested segments, with the exception of aorta and the proximal part of the caudal artery, showed concentration-dependent contractile responses to S6c which were further augmented after 5 days of culture. The ET-1-induced responses were only slightly affected by organ culture. Contractions induced by S6c were more enhanced in small arteries and veins than in larger arteries. Furthermore, the S6c-induced response was more pronounced in the mesenteric region as compared to the hindlimb. In fresh mesenteric arterial segments FR139317 (ETA receptor antagonist) and bosentan (ETA/ETB receptor antagonist) but not IRL 2500 (ETB receptor antagonist) shifted the ET-1-induced concentration-response curve in parallel to the right. In contrast, after organ culture the S6c-induced concentration-response curves were shifted parallel to the right in the following potency order: IRL 2500 > bosentan > FR139317. CONCLUSION: During normal conditions, the ETA receptor is the dominating mediator of endothelin-induced contraction in eight different vascular regions. Furthermore, this study indicates that most of the vessels have the ability to develop contractile ETB receptors and that this plasticity differs in vascular regions.
|
|
| 4. |
- Adner, Mikael, et al.
(författare)
-
Upregulation of a non-ETA receptor in human arteries in vitro
- 1995
-
Ingår i: Journal of Cardiovascular Pharmacology. - 1533-4023. ; 26:Suppl. 3, s. 314-316
-
Tidskriftsartikel (refereegranskat)abstract
- Receptor turnover may be a crucial part in the physiology of endothelin (ET). Incubation of vessel segments could be a possible method to demonstrate this. The aim was to study contractile responses of human omental arteries to different ET agonists at various periods after incubation at 37 degrees C in 5% CO2 and air. The maximum effect (Emax; percentage of contraction to 60 mM K+ buffer solution) and the potency of ET-1 were unaltered (pD2 = 8.82 +/- 0.06). The selective ETB agonist IRL 1620 demonstrated a negligible Emax in nonincubated segments (2.4 +/- 0.9%). After only 1 day of incubation the Emax was 51 +/- 23%, and it reached 114 +/- 53% after 5 days. The pD2 of IRL 1620 was stable throughout the incubation time (7.23 +/- 0.08). ET-3 showed a moderate Emax in nonincubated segments (55 +/- 18%), with a pD2 of 6.68 +/- 0.24. However, subsequent incubation revealed an increase of pD2 to 8.60 +/- 0.20 on the fifth day. The maximum contraction increased to 206 +/- 44%; this is equal to the contraction obtained in paired experiments with ET-1 (215 +/- 18%). These findings indicate modulation of endothelin receptor expression after incubation of vessel segments, and suggest the gradual appearance of a non-ETA receptor.
|
|
| 5. |
- Ekelund, Ulf, et al.
(författare)
-
Effects of the combined ETA and ETB receptor antagonist PD145065 on arteries, arterioles, and veins in the cat hindlimb
- 1995
-
Ingår i: Journal of Cardiovascular Pharmacology. - 1533-4023. ; 26:Suppl. 3, s. 211-213
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to describe in quantitative terms the effects of ETA and ETB receptor blockade on vascular tone (resistance) in large-bore arterial resistance vessels (> 25 microns), small arterioles (< 25 microns), and veins in the cat gastrocnemius muscle in vivo. In the muscle vascular bed, the combined ETA and ETB receptor antagonist PD145065 (1 mg/kg/min, intra-arterially) abolished the biphasic vascular responses (dilatation followed by constriction) to both ET-1 (0.4 microgram/kg/min, intra-arterially) and to the selective ETB receptor agonist IRL1620 (3.2 micrograms/kg/min, intra-arterially). In the cat femoral artery and vein in vitro, PD145065 competitively inhibited the contractile responses to both ET-1 and IRL1620. The contractile response to the latter agonist could be evoked only after long-term incubation of the vessels (37 degrees C for 5 days). These results indicate that PD145065 is a potent antagonist at both ETA and ETB receptors in vivo and in vitro. Therefore, this antagonist may prove useful for elucidating the possible physiologic and/or pathophysiologic roles of the endothelins. For example, it was shown that PD145065 had no effect on vascular tone in the resting state, indicating no role for the endothelins in the regulation of basal vascular tone in cat skeletal muscle.
|
|
| 6. |
- Lind, Henrik, et al.
(författare)
-
Selective increase of the contractile response to endothelin-1 in subcutaneous arteries from patients with essential hypertension
- 1999
-
Ingår i: Blood Pressure. - : Informa UK Limited. - 0803-7051 .- 1651-1999. ; 8:1, s. 9-15
-
Tidskriftsartikel (refereegranskat)abstract
- Endothelin-1 has been shown to contribute to basal vascular tone in man. Since endothelin-1 is a potent vasoconstrictor putatively involved in hypertension, we have compared the contractile responses of endothelin-1 and noradrenaline in relation to potassium chloride in subcutaneous resistance arteries from subjects with established essential hypertension with matched controls. Furthermore, with RT-PCR, the occurrence of mRNA for the ETA and ET(B) receptors was shown in the tunica media layer of subcutaneous arteries in controls and hypertensives. The maximum contractile response to endothelin-1 was significantly higher in the subcutaneous arteries of the hypertensives (by 88% with no change in potency) as compared to controls. The responses to noradrenaline, acetylcholine and potassium chloride did not differ between the groups. This selective increase in the contractile response to endothelin-1 might contribute to the development of essential hypertension.
|
|
| 7. |
- Uddman, Erik, et al.
(författare)
-
Cytokines induce increased endothelin ET(B) receptor-mediated contraction
- 1999
-
Ingår i: European Journal of Pharmacology. - 1879-0712. ; 376:3, s. 223-232
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of cytokines on the induction of contractile endothelin ET(B) receptors during organ culture was examined. Ring segments of rat superior mesenteric artery were used fresh or incubated for 24 h in Dulbecco's modified Eagle's medium alone, or with either interleukin-1beta, tumor necrosis factor-alpha (TNF-alpha) or interleukin-2. In fresh arterial segments there was no endothelin ET(B) receptor-induced contraction. After incubation, the selective endothelin ET(B) receptor agonist sarafotoxin 6c evoked a contraction of 22 +/- 6% relative to that induced by 60 mM K+. The endothelin ET(B) receptor-induced contraction was further increased to 125 +/- 25% and 157 +/- 29% by interleukin-1beta and TNF-alpha, respectively, while interleukin-2 did not alter the endothelin ET(B) receptor-induced contraction. The identity of the contractile receptor was confirmed as the endothelin ET(B) receptor by the use of an additional specific endothelin ET(B) receptor agonist, IRL 1620, and by antagonist experiments with FR 139317 and IRL 2500. The endothelin-1-induced contraction was not altered by either of the cytokines. Reverse transcriptase-polymerase chain reaction revealed increased levels of endothelin ET(B) mRNA, relative to endothelin ET(A) mRNA following organ culture, suggesting that contractile endothelin ET(B) receptors appear via de novo transcription. None of the cytokines changed the ratio of endothelin ET(A) and endothelin ET(B) receptor mRNA, indicating that the further increased sarafotoxin 6c-induced contraction is mediated through an enhancement of intracellular signalling mechanisms.
|
|
