Tachyphylaxis of human forearm vascular responses does not occur rapidly after exposure to isoproterenol.

Stein CM, Nelson R, Deegan R, He H, Inagami T, Frazer M, Badr KF, Wood M, Wood AJ
Hypertension. 1995 25 (6): 1294-300

PMID: 7768576 · DOI:10.1161/01.hyp.25.6.1294

In vitro and limited in vivo data suggest that rapid desensitization of beta-adrenoceptor responses occurs after exposure to agonist. Tachyphylaxis to a beta-adrenoceptor agonist would represent a potentially important mechanism for the short-term regulation of vascular tone. The effects of a 4-hour infusion of 400 ng/min intra-arterial isoproterenol on forearm blood flow and presynaptic beta-adrenoceptor-mediated norepinephrine release were determined in eight healthy volunteers. Intra-arterial isoproterenol at 400 ng/min resulted in a significant increase in forearm blood flow in all eight subjects at all time points, with no evidence of tachyphylaxis. In fact, forearm blood flow after 4 hours of the isoproterenol infusion (22.8 +/- 3.3 mL/100 mL per minute) was significantly greater than after 7 minutes (14.6 +/- 2.8 mL/100 mL per minute), 15 minutes (15.4 +/- 2.4 mL/100 mL per minute), and 30 minutes (17.4 +/- 3.0 mL/100 mL per minute) of the infusion (P < .05). Similarly, presynaptic beta-adrenoceptor responses showed no evidence of tachyphylaxis, so forearm norepinephrine spillover values after 7 minutes (6.6 +/- 0.94 ng/min), 15 minutes (7.6 +/- 1.5 ng/min), and 4 hours (8.8 +/- 1.1 ng/min) of isoproterenol infusion were increased and similar. Minimal systemic effects were observed, and there was no evidence of tolerance, there being no difference in heart rate after 7 minutes (70.7 +/- 2.7 beats per minute) and 4 hours (72.2 +/- 3.6 beats per minute) of isoproterenol infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

MeSH Terms (11)

Adult Angiotensin II Forearm Humans Isoproterenol Male Muscle, Smooth, Vascular Receptors, Adrenergic, beta Regional Blood Flow Tachyphylaxis Time Factors

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