Page 282 - Color_Atlas_of_Physiology_5th_Ed._-_A._Despopoulos_2003

stimuli (! p. 170), whereas the release of me- permeability of blood vessels (inflammation).
latonin is subject to afferent neuron control PGD 2 induces bronchoconstriction. PGI 2 (pros-
(! p. 334). tacyclin) synthesized in the endothelium, is
Some of these hormones (e.g., angiotensin vasodilatory and inhibits platelet aggregation.
II) and tissue hormones or mediators exert TXA 2, on the other hand, occurs in platelets,
paracrine effects within endocrine and ex- promotes platelet aggregation and acts as a va-
ocrine glands, the stomach wall, other organs, soconstrictor (! p. 102). 11,12-EpETrE has a
and on inflammatory processes. Bradykinin vasodilatory effect (= EDHF, ! p. 214).
(! pp. 214 and 236), histamine (! pp. 100
and 242), serotonin (5-hydroxytryptamine, Hormones (h.) of the hypothalamus and pituitary
! p. 102) and eicosanoids are members of this Name* Abbreviation/synonyme
group.
Eicosanoids. Prostaglandins (PG), Hypothalamus
thromboxane (TX), leukotrienes and epoxyei- The suffix “-liberin” denotes releasing
cosatrienoates are eicosanoids (Greek ει!%σι = h. (RH) or factor (RF); “-statin” is used for release-
inhibiting h. (IH) or factors (IF)
twenty [C atoms]) derived in humans from the
fatty acid arachidonic acid (AA). (Prostaglan- Corticoliberin Corticotropin RH, CRH, CRF
Gonadoliberin
Gonadotropin RH, Gn-RH; ICSH
dins derived from AA have the index number Prolactostatin Prolactin IH, PIH, PIF, dopamine
2). AA occurs as an ester in the phospholipid Somatoliberin Somatotropin RH, SRH, SRF,
layer of the cell membranes and is obtained GHRH, GRH
from dietary sources (meat), synthesized from Somatostatin** Somatotropin (growth h.) IH, SIH Hormones
linoleic acid, an essential fatty acid, and re- Thyroliberin Thyrotropin RH, TRH, TRF
leased by phospholipase A 2 (! p. 252) . Anterior lobe of the pituitary
Pathways of eicosanoid synthesis from arachidonic Corticotropin Adrenocorticotropic h. (ACTH)
acid (AA): Follitropin Follicle-stimulating h. (FSH)
1. Cyclooxygenase pathway: Cyclooxygenase (COX)-1 Lutropin Luteinizing h. (LH), interstitial
and COX-2 convert AA into PGG 2, which gives rise to cell-stimulating h. (ICSH)
PGH 2, the primary substance of the biologically ac- Melanotropin α-Melanocyte-stimulating h.
tive compounds PGE 2, PGD 2, PGF 2α, PGI 2 (prostacy- (α-MSH), α-melanocortin
clin) and TXA 2. COX-1 and 2 are inhibited by non- Somatotropin Somatotropic h. (STH), growth h.
steroidal anti-inflammatory drugs (e.g., Aspirin!). (GH)
2. Lipoxygenase pathway: Leukotriene A 4 is synthe- Thyrotropin Thyroid stimulating h. (TSH)
sized from AA (via the intermediate 5-HPETE = 5-hy-
droperoxyeicosatetraenoate) by way of 5-lipoxy- Prolactin PRL, lactogenic (mammotropic)
genase (especially in neutrophilic granulocytes). h.
Leukotriene A 4 is the parent substance of the Posterior lobe of the pituitary
leukotrienes C 4, D 4 and E 4. The significance of 12- Oxytocin –
lipoxygenase (especially in thrombocytes) is not yet
clear, but 15-lipoxygenase is known to produce va- Adiuretin Anti-diuretic h. ADH,
soactive lipoxins (LXA 4, LXB 4). (arginine-) vasopressin (AVP)
3. Cytochrome P450-epoxygenase produces epoxyei- ** Names generally recommended by IUPAC-IUB
cosatrienoates (EpETrE = EE). Committee on Biochemical Nomenclature.
Typical effects of eicosanoids: ** Also synthesized in gastrointestinal organs, etc.
PGE 2 dilates the bronchial and vascular
musculature (and keeps the lumen of the fetal
ductus arteriosus and foramen ovale open;
! p. 220), stimulates intestinal and uterine
contractions, protects the gastric mucosa
(! p. 242), inhibits lipolysis, increases the glo-
merular filtration rate (GFR), plays a role in
fever development (! p. 224), sensitizes noci-
ceptive nerve endings (pain) and increases the 269

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