Apw

Endothelial cell

Intercellular /p. cement

Arteriole

Smooth muscles

Intercellular /p. cement

Arteriole

Smooth muscles

Precapillary sphincters

Arterial capillary

Thoroughfare channel

Venous capillary

Enlargement of true capillary

Enlargement of true capillary

Venule

FIGURE 15-6—Continued

Precapillary sphincters

Arterial capillary

Thoroughfare channel

Venous capillary where it acts within seconds. In both locations, the biological response generated by angiotensin II is mediated as a consequence of its binding to high-affinity membrane receptors; these receptors have been cloned and found to have a seven transmembrane domain that is linked to a G protein (see Chapter 1). The immediate postangiotensin II receptor-binding signal transduction events include the elevation of both IP3 and intracellular Ca2+ concentrations.

1. Aldosterone Biosynthesis

The site of production of the mineralocorticoid aldosterone is the adrenal zona glomerulosa cell, which employs a variety of signal transduction mechanisms that include receptors for angiotensin II, ACTH, dopamine, and atrial natriuretic peptide as well as a K+-

TABLE 15-4 Classification of Blood Pressure Levels

Classification"

Systolic (mm Hg)

Diastolic (mm Hg)

Normal

<130

<85

High normal

0 0

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