Vascular Smooth Muscle Contraction

The intravenous injection of angiotensin II results in a sharp rise in systolic and diastolic pressures. The response is consistently reproducible when small doses of an-giotensin II are injected; however, larger amounts of the peptide produce tachyphylaxis (loss of response on repeated administration). The mechanism underlying tachy-phylaxis to angiotensin II is unknown, but it may involve receptor internalization and/or desensitization. Subcutaneous and intramuscular injections are much less potent and have a longer duration of action than do comparable doses given intravenously. Infusions that cause an immediate pressor response tend to result in tachyphylaxis over several hours. On a molar basis, angiotensin II is about 40 times as potent as norepinephrine. The pressor response to angiotensin II is caused by its direct receptor-mediated effect on vascular smooth muscle. The peptide stimulates the formation of the second messenger inositol 1,4,5-triphosphate, which results in a release of intracellular Ca++ and ultimately smooth muscle contraction.

Was this article helpful?

0 0
How To Bolster Your Immune System

How To Bolster Your Immune System

All Natural Immune Boosters Proven To Fight Infection, Disease And More. Discover A Natural, Safe Effective Way To Boost Your Immune System Using Ingredients From Your Kitchen Cupboard. The only common sense, no holds barred guide to hit the market today no gimmicks, no pills, just old fashioned common sense remedies to cure colds, influenza, viral infections and more.

Get My Free Audio Book

Post a comment