BIPN 100 Lecture Notes - Lecture 12: Autocrine Signalling, Lipophilicity, Aldosterone
13 Jun 2018
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BIPN 100 Lecture 12
4/30/2018
• Hormones
o Chemical signals that are secreted by a cell or group of cells
o They are transported by blood
▪ Transported to a distant target
▪ They have a slower response compared to neurons
▪ They activate physiological responses at low concentration
o Bind to target cell receptors and initiate biochemical responses
▪ One hormone may act on multiple tissues
▪ Effects may vary in different tissues, which is determined by the receptor
o Pheromones elicit a physiological or behavioral response on other organisms of
the same species
o Paracrine: target is nearby
o Autocrine: targets itself
o Neurocrine: released by a neuron
▪ E.g. release of epinephrine into the blood
• Types of hormones
o Steroids
▪ Cholesterol derived
▪ Made in a few organs: adrenal cortex (cortisone and aldosterone),
gonads and placenta (estrogen, progesterone, testosterone)
▪ Are lipophilic and easily cross membranes
• Not very soluble in plasma
• Bind to carrier proteins in the blood, thus having a longer half-life
(can be active for a longer period of time)
▪ Cytoplasmic or nuclear receptors
• Genomic effect to activate or repress genes for protein synthesis
• Are slower acting
▪ Cell membrane receptors
• Non0genomic responses
o Amino-acid or amines
▪ Derived from tryptophan (e.g. melatonin) or tyrosine (catecholamines
and thyroid hormones)
o Peptides or proteins
▪ Water soluble
▪ Dissolve easily in the ECF for transport
▪ Have a short half-life (several minutes)
▪ Peptide: short chains of amino acids like ADH and oxytocin
▪ Protein hormones: long chains of amino acids (like insulin and HGH)
o Eicosanoids
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▪ Roles: inflammatory response, intensity and duration of pain/ever,
reproductive unction (induction of labor), inhibitor of gastric acid
secretion, BP control, activation/inactivation of platelet aggregation
▪ Produced from oxidation of Arachidonic acid (20 carbon polyunsaturated
fatty acid)
• Thromboxanes: induce blood clot formation
• Prostacyclins: reduce blood clot formation
o Both are COX prostaglandins
• LOX leukotrienes: mediate inflammation, and can cause
inflammation/constriction of bronchioles
• Lipid soluble vs. water soluble
o Lipid
▪ Can cross bilayer
▪ Have to be transported with a protein carrier in the blood
▪ Go into the cell and bind to cause transcription or translation
▪ Are steroids and thyroid hormones
o Water
▪ Can go without a carrier in the blood
▪ Cannot cross bilayer: must bind to a membrane receptor
▪ Generally, these receptors are coupled with g-proteins (GPCRs)
▪ Start a bunch of cellular responses within the cell via a secondary
messenger
▪ Are the peptides and proteins, and catecholamines
• Mechanism of action of eicosanoids
o Are lipid soluble, but use membrane bound receptors (e.g. Gs,I,q)
o Most act locally
• Termination of hormone action
o Hormones in the blood are degraded into inactive metabolites
▪ Uptake by specific receptors
▪ Enzymes in the liver and kidneys break them down
▪ Metabolists excreted in the bile or urine
• Urine=hydrophilic (peptides, proteins, catecholamines)
• Bile= lipophilic (steroid and thyroid hormones)
• KNOW THE PARATHYROID GLANDS
o Sense the concentration of calcium in the plasma, and release parathyroid
hormone
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