Page 508 - Clinical Hematology_ Theory _ Procedures ( PDFDrive )

492 PART 7 ■ Principles and Disorders of Hemostasis and Thrombosis

n interleukin-1 (IL-1), vir l in ection n tr ns or tion,

TABLE 25.3 Endothelial Functions b cteri l toxins, n cholesterol n oxi tively o if e

lipoproteins.

Angiogenesis Synthesis of stromal components Disruption o the en otheliu irectly ctiv tes ll our
co ponents o he ost sis. A er this event, the ollowing

Coagulation Vascular tone regulation events t ke pl ce:

In ammation Special metabolic functions* 1. Initi lly, r pi v soconstriction or up to 30 inutes

Immune responses re uces bloo ow n pro otes cont ct ctiv tion o

pl telets n co gul tion ctors.
*Transporting molecules from the vascular lumen to the subendothelium,
producing angiotensin-converting enzyme, and binding lipoproteins, high- 2. In the secon ph se, pl telets here i e i tely to the

density lipoproteins, and low-density lipoproteins. expose suben otheli l connective tissue, p rticul rly

coll gen. T e ggreg te pl telets enh nce sust ine v so-
constriction by rele sing thro box ne A n v so ctive
2
The Endothelins ines, inclu ing serotonin n epinephrine.
3. In the thir ph se, co gul tion is initi te through the
In 1985, ily o pepti es, n e the endothelins, w s intrinsic system or the extrinsic system.

isol te n i entif e . T e three e bers o the ily— 4. Fin lly, f brinolysis occurs ollowing the rele se o tissue

en othelin-1, en othelin-2, n en othelin-3— re pro- pl s inogen ctiv tors (t-PAs) ro the v scul r w ll.

uce in v riety o tissues, where they ct s o ul tors o Fibrinolytic re ov l o excess he ost tic teri l is nec-

v so otor tone, cell proli er tion, n hor one pro uction. ess ry to reest blish v scul r integrity.

En othelin-1 is the only ily e ber pro uce in

en otheli l cells n is lso pro uce in v scul r s ooth

uscle cells. It is not store in secretory gr nules within Maintenance of Vascular Integrity

en otheli l cells. Sti uli such s hypoxi , ische i , or she r

stress in uce the RNA n synthesis n secretion o V scul r integrity or the resist nce to vessel isruption

en othelin-1 within inutes. T e h l -li e is pproxi tely requires three essenti l ctors. T ese ctors re circul t-

4 to 7 inutes. ing unction l pl telets, renocorticosteroi s, n scorbic

En othelin-2 is pro uce pre o in ntly within the ki - ci . A l ck o these ctors pro uces r gility o the vessels,

ney n intestine, with s ller ounts pro uce in the which kes the prone to isruption. M inten nce o v s-

yoc r iu , pl cent , n uterus. T e cells o origin re not cul r integrity through the he ost tic process epen s on

cle r. En othelin-2 h s no unique physiologic l unctions s the events previously escribe . T e i port nce o these

co p re with en othelin-1. re ctions v ries with vessel size (e.g., c pill ries se l e s-

En othelin-3, like en othelin-1, circul tes in the pl s , ily bec use o v soconstriction). T e integrity o rterioles

but its source is not known. En othelin-3 h s been oun in n venules epen s on v soconstriction, the or tion o

high concentr tions in the br in n y regul te i port nt plug o use pl telets over the injury, n the or tion

unctions, such s proli er tion n evelop ent in neurons o f brin clot. Arteries, bec use o their thick w lls, re the

n strocytes. It lso is oun throughout the g strointesti- ost resist nt to blee ing; however, he orrh ge ro these

n l tr ct n in the lungs n ki neys. vessels is the ost ngerous. V soconstriction is o ulti te

All three en othelins bin to two types o receptors (A i port nce in ge rteries. Veins, which cont in 70%

n B) on the cells o ny li n species, inclu ing o the bloo volu e, y rupture with slight incre se in

hu ns. En othelin-A receptors re expresse bun ntly hy rost tic pressure.

on v scul r s ooth uscle cells n c r i c yocytes.

T ese receptors e i te the v soconstrictor ction o en o- NOTE: This is a good time to review the de nitions of Key

thelin-1, lthough en othelin-B receptors y contribute Terms in the Glossary and ash cards using .

to this ction in so e v scul r be s. ype B receptors re This is also a good time to complete the Review Questions

expresse pre o in tely on en otheli l cells n to uch related to the preceding content.

lesser extent on v scul r s ooth uscle cells. En othelin-B

receptors bin en othelin-1 n en othelin-3 with si il r

nity.

THROMBOPOIESIS
Endothelial Dysfunction

M ni est tions, collectively ter e endothelial dysfunction, M ture pl telets (thro bocytes) (Fig. 25.2), et bolic lly

pl y n i port nt role in the initi tion, progression, n ctive cell r g ents, re the secon critic l co ponent in

clinic l co plic tions o v rious or s o in tory n the inten nce o he ost sis. T ese nucle r cells circu-

egener tive v scul r ise ses. V rious sti uli o en othe- l te in the peripher l bloo er being pro uce ro the

li l ys unction h ve been i entif e , inclu ing i uno- cytopl s o bone rrow megakaryocytes, the l rgest cells

regul tory subst nces such s tu or necrosis ctor ( NF) oun in the bone rrow.