Reserpine-induced changes in cardiac adrenergic receptors

1984 ◽  
Vol 62 (1) ◽  
pp. 23-26 ◽  
Author(s):  
Jamshid Latifpour ◽  
John H. McNeill

Using radioligand binding techniques, the effect of reserpine pretreatment on ventricular adrenergic receptors from guinea pig was studied. [3H]Prazosin and [3H]dihydroalprenolol were used to label α1- and β-adrenergic receptors, respectively. Administration of 2.5 mg/kg reserpine for 2 days caused a significant increase in the number of β-adrenergic receptors with no effect on their affinity to respective ligands. Similar reserpine pretreatment did not affect either density or affinity of α1-adrenergic receptors for ligands. The results may explain the previous report from our laboratory in which an identical reserpine pretreatment selectively enhanced the inotropic responsiveness of the working guinea pig heart to isoproterenol.


1987 ◽  
Vol 253 (5) ◽  
pp. H1159-H1166 ◽  
Author(s):  
A. S. Maisel ◽  
H. J. Motulsky ◽  
M. G. Ziegler ◽  
P. A. Insel

We have used radioligand binding techniques and subcellular fractionation to assess whether changes in expression of myocardial alpha 1- and beta-adrenergic receptors are mediated by a redistribution of receptors between various membrane fractions. Three fractions were prepared from the left ventricles of guinea pigs that underwent either 1 h of ischemia or injection of epinephrine (0.25 mg/kg ip): a crude membrane, a purified sarcolemma, and a light vesicle fraction. In control animals alpha 1-adrenergic receptors ([3H]prazosin binding) in light vesicles was only 25% of the total alpha 1-receptor density found in sarcolemmal and light vesicle fractions as compared with 50% for beta-adrenergic receptors ([125I]iodocyanopindolol binding sites). Although ischemia was associated with a 53% decrease in the number of light vesicle beta-adrenergic receptors and a 42% increase in the number of sarcolemma beta-receptors (P less than 0.05), there was no change in the number of light vesicle alpha 1-receptors, even though the number of sarcolemmal alpha 1-receptors increased 34%. Epinephrine treatment promoted internalization of beta-adrenergic receptors; sarcolemma beta-receptors decreased 37% and light vesicle beta-receptors increased 28% (P less than 0.025). For alpha 1-receptors, epinephrine treatment decreased the number of sarcolemmal receptors 41% (P less than 0.025) but failed to increase the number of receptors in the light vesicle fraction. The changes in receptor binding to beta-adrenergic receptors in sarcolemmal fractions were mirrored by parallel changes in isoproterenol-stimulated adenylate cyclase activity. These results indicate that alpha 1- and beta-adrenergic receptors may undergo a different cellular itinerary in guinea pig myocardium.(ABSTRACT TRUNCATED AT 250 WORDS)



1989 ◽  
Vol 160 (3) ◽  
pp. 751-757 ◽  
Author(s):  
Christos G. Hatjis ◽  
Donald R. Koritnik ◽  
David M. Grogan


1994 ◽  
Vol 72 (4) ◽  
pp. 335-343 ◽  
Author(s):  
Mark M. Knuepfer ◽  
Carrie A. Branch ◽  
David M. Wehner ◽  
Qi Gan ◽  
Dung Hoang

The pressor response to cocaine is a consequence of mesenteric vasoconstriction and hindquarters vasodilation as a result of activation of α1- and β-adrenergic receptors, respectively. In the present study, evidence for additional, nonadrenergic effects of cocaine-induced changes in regional blood flow was obtained using pulsed Doppler flowmetry in conscious rats. Cocaine produced dose-dependent initial peaks (within 1 min) in mean arterial pressure concomitant with an increase in hindquarters and mesenteric vascular resistance. The sustained, modest pressor response was associated with hindquarters vasodilation and bradycardia. The cocaine-induced vasodilation was enhanced by pretreatment with indomethacin (5 mg/kg), prevented by ibuprofen (12.5 mg/kg) or 3-amino-1-[m-(trifluoromethyl)-phenyl]-2-pyrazoline (BW755C, 10.5 mg/kg) pretreatment, and unaffected by meclofenamate administration (2.5 mg/kg). Equipotent local anesthetic doses of procaine produced equivalent hindquarters vasodilator responses and more modest pressor responses. Dial–urethane anesthesia did not affect hindquarters vasodilation in response to cocaine or procaine but did reduce the mesenteric vasoconstrictor and pressor responses. These data demonstrate that the cocaine-induced hindquarters vasodilation is not mediated solely by β-adrenergic receptors but is also dependent upon eicosanoids. Furthermore, the cocaine-induced vasodilation may be due, in part, to a direct local anesthetic effect but is not dependent upon a locomotor or behavioral stress induced increase in blood flow.Key words: anesthesia, eicosanoids, arterial pressure, hindquarters and mesenteric vascular resistances, pulsed Doppler flowmetry.



1981 ◽  
Vol 241 (1) ◽  
pp. H18-H25
Author(s):  
K. Schror ◽  
P. Kohler ◽  
M. Muller ◽  
B. A. Peskar ◽  
P. Rosen

A preparation of an isolated platelet-perfused guinea pig heart is described, which was utilized to study prostacyclin-thromboxane interrelationships. Infusion of washed human platelets (4 X 10(8)/min) through the coronary vascular bed stimulated the vascular PGI2 production from 114 +/- 27 to 350 +/- 30 pg/ml (P less than 0.01) and was associated with a significant increase in platelet cAMP from 1.2 +/- 0.4 to 2.6 +/- 0.9 pmol/10(8) platelets (P less than 0.05). Administration of arachidonic acid (AA) (45 micrograms) to the system led to a further increase (eight- to ninefold) of PGI2 and yielded marked thromboxane formation (20-25 ng/ml). Treatment of the hearts with aspirin (1 mM) prevented the PGI2 formation and AA-induced increase in platelet cAMP. Treatment of platelets with aspirin prevented thromboxane formation but did not influence AA-induced changes in platelet cAMP and vascular PGI2 production. Bioassay data of PGI2 and rabbit aortic contracting substance gave results comparable to radioimmunoassay of 6-keto-PGF1 alpha and thromboxane B2. AA always decreased the coronary vascular resistance whether thromboxanes were formed or not.



1986 ◽  
Vol 111 (2) ◽  
pp. 263-270 ◽  
Author(s):  
J. M. Fyles ◽  
M. A. Cawthorne ◽  
S. L. Howell

ABSTRACT The sympathetic nervous system is believed to play a part in the control of insulin release from the pancreatic islets of Langerhans. Stimulation of α-adrenoceptors is thought to inhibit the release of insulin whereas stimulation of β-adrenoceptors enhances insulin release. The present experiments were conducted to establish the existence of β-adrenergic receptors on guinea-pig and rat islet cells and to quantify them using the selective β-adrenergic ligands [3H]dihydroalprenolol (DHA) and [125I]cyanoiodopindolol (CYP). Guinea-pig islets had 62 fmol β-adrenoceptors/mg protein using [3H]DHA, corresponding to 43 700 binding sites/cell and 25 fmol β-adrenoceptors/mg protein using [125I]CYP, corresponding to 17 400 sites/cell. Rat islet cells were found to have 4·6 fmol β-adrenoceptors/mg protein using [125I]CYP, corresponding to 7200 sites/cell. Adenylate cyclase activation exhibited a positive dose–response relationship when exposed to the β-adrenoceptor agonist isoprenaline, with a maximum response (190 ± 21% above basal) at 10 μmol isoprenaline/l. This response was abolished with 1 μmol/l of the β-adrenergic antagonist 1-alprenolol. Insulin secretion in the presence of 10 mmol glucose/l, but in the absence of the α-adrenoceptor blocker phentolamine, was not affected by 10 μmol isoprenaline/l. However, perifusion experiments showed that secretion of insulin from isolated rat islets in the presence of 10 mmol glucose/l was significantly increased (332%) by 10 μmol isoprenaline/l in the presence of 10 μmol phentolamine/l. These results suggest that binding of selective radio-labelled ligands occurs to β-adrenergic receptors on the B cell surface of the islets of Langerhans, and that these receptors are functionally coupled to insulin secretion through modulation of adenylate cyclase activity. J. Endocr. (1986) 111, 263–270



2003 ◽  
pp. 329-343
Author(s):  
Cheryl D. Dunigan ◽  
Patricia K. Curran ◽  
Peter H. Fishman


1997 ◽  
Vol 11 (2) ◽  
pp. 111-116 ◽  
Author(s):  
D. Scherrer ◽  
E. Lach ◽  
Y. Landry ◽  
JP Gies


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