Endocrine hormones act from a distance and paracrine hormones act locally. The renal enzyme renin converts angiotensinogen into angiotensin I. The lung enzyme, ACE, converts angiotensin I into active angiotensin II. Angiotensin II is an active vasoconstrictor that increases blood pressure. Angiotensin II also stimulates aldosterone release from the adrenal cortex, causing the collecting duct to retain Na+, which promotes water retention and a longer-term rise in blood pressure. ADH promotes water recovery by the collecting ducts by stimulating the insertion of aquaporin water channels into cell membranes. Endothelins are elevated in cases of diabetic kidney disease, increasing Na+ retention and decreasing GFR. Natriuretic hormones, released primarily from the atria of the heart in response to stretching of the atrial walls, stimulate Na+ excretion and thereby decrease blood pressure. PTH stimulates the final step in the formation of active vitamin D3 and reduces phosphate reabsorption, resulting in higher circulating Ca++ levels.
endothelins
group of vasoconstrictive, 21-amino acid peptides; produced by endothelial cells of the renal blood vessels, mesangial cells, and cells of the DCT
1. What hormone directly opposes the actions of natriuretic hormones?
A) renin
B) nitric oxide
C) dopamine
D) aldosterone
D
2. Which of these is a vasoconstrictor?
A) nitric oxide
B) natriuretic hormone
C) bradykinin
D) angiotensin II
D
3. What signal causes the heart to secrete atrial natriuretic hormone?
A) increased blood pressure
B) decreased blood pressure
C) increased Na+ levels
D) decreased Na+ levels
A
1. What organs produce which hormones or enzymes in the renin–angiotensin system?
The liver produces angiotensinogen, the lungs produce ACE, and the kidneys produce renin.
2. PTH affects absorption and reabsorption of what?
PTH affects absorption and reabsorption of calcium.