Polypeptides Flashcards
What are autacoids?
Autacoids are biological factors that act like local hormones, including peptides and other molecules that modulate physiological functions.
Examples of autacoids include renin, angiotensin, kinins, vasopressin, natriuretic peptides, endothelins, and various neuropeptides.
What are kinins?
Kinins are potent vasodilator peptides formed by the action of enzymes called kallikreins on precursors known as kininogens.
Kinins play significant roles in blood pressure regulation and inflammation.
What are the two forms of kininogens found in plasma?
The two forms of kininogens found in plasma are:
* Low Molecular Weight (LMW) kininogens (80-85%)
* High Molecular Weight (HMW) kininogens (15-20%)
What is the predominant kinin in plasma?
Bradykinin is the predominant kinin found in plasma.
Lysylbradykinin is the major urinary form of kinin.
What are the primary actions of kinins?
The primary actions of kinins include:
* Marked vasodilation in vascular beds
* Vasoconstriction on veins
* Contraction of visceral smooth muscle
* Transient decrease in blood pressure
* Increased capillary permeability and tissue edema
* Role in inflammation and pain production
Which receptors do kinins primarily act on?
Kinins primarily act on B1 and B2 receptors.
Bradykinin has the highest affinity for B2 receptors.
How are kinins metabolized?
Kinins are rapidly metabolized by kininases with half-lives of approximately 15 seconds.
Kininase I is synthesized in the liver, while Kininase II is found in plasma and vascular endothelial cells.
What is the role of vasopressin (ADH)?
Vasopressin plays a vital role in regulating blood pressure by reabsorbing water in the kidneys and has vasoconstrictor action at low doses.
It is particularly important in conditions like cardiac disease and orthostatic hypotension.
What are the three types of natriuretic peptides?
The three types of natriuretic peptides are:
* Atrial natriuretic peptide (ANP)
* Brain natriuretic peptide (BNP)
* C-type natriuretic peptide (CNP)
What is the effect of atrial natriuretic peptide (ANP)?
ANP increases sodium excretion, urine flow, inhibits secretion of renin, aldosterone, and vasopressin, and decreases arterial blood pressure via vasodilation.
ANP is synthesized primarily in atrial cells.
What are the actions of endothelins?
Endothelins are potent vasoconstrictors that cause dose-dependent vasoconstriction, increase blood pressure, and have various effects on the endocrine system and CNS.
They include ET1, ET2, and ET3, which are distributed widely in the body.
What is the mechanism of action for natriuretic peptides?
Natriuretic peptides act via surface receptors ANPa, ANPb, and ANPc, leading to various physiological effects.
They are metabolized in the lungs, kidneys, and liver by neutral endopeptidases.
True or False: Kallikreins are found only in plasma.
False
Kallikreins are found in plasma and several tissues including kidneys, pancreas, and intestines.
Fill in the blank: Bradykinin is ______ times as potent as histamine.
10
What drug inhibits kinin synthesis by inhibiting kallikrein?
Aprotinin.
What is the primary function of the B1 receptor in relation to kinins?
The B1 receptor participates in inflammation and is thought to be responsible for long-term effects such as collagen synthesis and cell multiplication.
What is the primary mechanism for the clearance of endothelins from circulation?
Endothelins are rapidly cleared from circulation by enzymes and by binding to ETb receptors.
What type of drug is bosentan?
Bosentan is a nonselective inhibitor of ETa and ETb receptors.
It is used in the treatment of pulmonary arterial hypertension (PAH).
What are ETa and ETb?
Receptors that mediate responses blocked by endothelin antagonists
ETa and ETb are important in cardiovascular regulation.
What is the role of phosphoramidon?
Blocks endothelin converting enzyme
It is used in the treatment of pulmonary arterial hypertension (PAH).
List the effects of endothelin antagonists.
- Lower blood pressure
- Decrease cardiac hypertrophy
- Improve heart failure
- Affect atherosclerosis
- Influence coronary artery disease
- Role in myocardial infarction (MI)
These effects make them significant in cardiovascular treatments.
Name some non-selective ETa inhibitors.
- Bosentan
- Sitaxentan
- Ambrisentan
These are useful in treating heart failure and hypertension.
What is tezosentan under study for?
Acute heart failure treatment
It is an analogue of bosentan.
What are common side effects of endothelin antagonists?
- Hypotension
- Tachycardia
- Facial flushing or edema
- Headaches
- Gastrointestinal effects
- Teratogenicity
These side effects can limit their use in certain populations.
What is vasoactive intestinal peptide (VIP)?
A 28 amino acid peptide related to secretin and glucagon
It acts as a neurotransmitter and neuromodulator.
Where is VIP widely distributed?
- CNS
- PNS
- GIT
- Heart
- Lungs
- Kidneys
- Thyroid gland
Its widespread presence highlights its physiological significance.
What effect does VIP have on blood vessels?
Causes marked vasodilation
This includes coronary vasodilation and increased heart effects.
What receptors does vasoactive intestinal peptide act on?
- VPAC1
- VPAC2
These receptors are G-protein linked and increase cAMP.
True or False: Substance P is a neurotransmitter in both the CNS and GIT.
True
It also acts as a local hormone.
What are the receptors for Substance P?
- NK1
- NK2
- NK3
These receptors mediate various physiological responses.
What are the effects of neurotensin?
- Vasodilation
- Hypotension
- Increased vascular permeability
- Modulation of dopamine neurotransmission
- Inhibition of gastric acid and motility
Its actions can be both central and peripheral.
Where is neurotensin found?
- CNS
- GIT
- Circulation
It acts as a neurotransmitter and neuromodulator.
What is the function of calcitonin gene-related protein (CGRP)?
Causes hypertension and suppression of feeding
It has diverse roles in both central and peripheral systems.
What are the receptors for CGRP?
- CGRP1
- CGRP2
These receptors play a role in its physiological effects.
What is adrenomedullin’s primary effect in the body?
Causes vasodilation
It is involved in various physiological processes, including sodium excretion.
What family does neuropeptide Y belong to?
The tachykinin family
Other members include peptide YY and pancreatic polypeptide.
What are the implications of neuropeptide Y?
- Increased feeding
- Hypotension
- Hypothermia
- Respiratory depression
It has significant roles in energy balance and cardiovascular regulation.
What is urotensin II?
A potent vasoconstrictor of smooth muscles
It may cause vasodilation in some areas.
What is palosuran under study for?
Hypertension, heart failure, and renal failure
It acts as an antagonist to urotensin II.
