Endocrinology, lecture on Renin-Angiotensin System
USD Department of Biology
Endocrinology
Summers
Hormones
Endocrine Glands
Receptors
Homeostasis
2nd Messengers
Nuclear Receptors
Genetic Regulation
Hormone Synthesis
Receptor Regulation
Hypothalamo-Hypophysial Communication
Tropic Hormones
Neurohypophysial Nonapeptides
Thyroid Axis
Steroids
Adrenal Axis
Adrenal Medulla
Osmotic-Pressure Balance
Reproductive Endocrinology
Prolactin
Somatic Axis
Growth Factors
Immune Factors
Ca++, PO4 Homeostasis
Pancreatic Hormones
GI Hormones
Guts 'n Brains
Brain Hormones
Neurosteroids
Neuropeptides
Endocrine Evolution
Figures for Endocrionology
text:Vertebrate Endocrinology5th Edition - David O. Norris:
Read pages 273-279 for this lecture
acronyms    end
XVIII. Osmo/pressure balance  			

	A. Renin - Angiotensin - Aldosterone system has 2 major functions


		1. osmotic balance


		2. arterial pressure


	B. Juxtaglomerular Apparatus		   


		1. smooth muscle cells of the afferent arteriole, which are next to
		   the distal tubule (just before the glomerulus) secrete renin (an enzyme)


			a. endocrine cells


		2. Macula Densa: cells of the distal tubule
		   next to the afferent arteriole


			a. chemoreceptor


		3. Adrenergic and cholinergic innervation


	C. Regulation				
	

		1. Renin is secreted when


			a. Na+ uptake across the macula densa is low


			b. pressure in the afferent arteriole is low


			c. b2 adrenergic stimulation = sympathetic activation


		2. Renin is an enzyme which converts angiotensinogen (13 aa peptide
		   from the liver) into Angiotensin I in the blood


			a. Ang1  is a decapeptide


			b. Ang1  stimulates catecholamine release from adrenal


		3. Converting Enzyme (ACE) from the lung, kidney, liver + vascular
		    endothelia removes 2  C-terminal  aa


			a. Angiotensin II (Ang2 = 8 aa)


		4. Ang2 stimulates Aldosterone production
		    + release from adrenal cortex
												

			a. stimulates AVP release from the hypothalamus + catecholamines
			   from SNS and adrenal medulla


				i. AVP also stimulated by osmoreceptors 


				ii. Ang2 + AVP stimulate dipsogenic response


			b. is the strongest known vasoconstrictor


			c. is converted to Angiotensin III (Ang3 = 7 aa)


		5. Aldosterone stimulates Na+ reabsorption/conservation
		    and K+ excretion


			a. mostly in the kidney but also in sweat and salivary glands


			b. aldosterone is also stimulated by ACTH and  [K+]



		6. Feedback


			a. Ang2 & 3 suppress secretion of renin


			b. indirect negative feedback


				i. aldosterone ®+  Na+ reabsorption


				ii. Epi/NE ®+ a1 adrenergic receptors ®  BP


				iii. drinking, antidiuresis ®  BP


			c. Angiotensin I ®+  Epi/NE (adrenal medulla) ® b2 ®+   renin


				i. indirect positive feedback


			d. aldosterone does not inhibit ACTH

			

	D. Atrionatriuretic Hormone (= ANP, ANF, auriculin, atriopeptin),
	    Brain natriuretic peptide (BNP), and CNP (also from brain)


		1. ANP 28 aa from a 151 aa preprohormone made in secretory cells or
		   the right atrial myometrium


			a. BNP (2 types 26 & 32 aa)


		2. bind to membrane receptors coupled to GC/cGMP 2nd messenger system


			a. ANP + BNP bind peripheral receptors equally


			b. brain receptors bind BNP or CNP > ANP


			
		3. NPs cause diuresis (H2O excretion) and Na+ excretion


			a. also  Cl-, PO4-, Ca++ excretion 


			b. stimulated directly by  plasma Na+


		4. relax smooth muscle


			a. vasodilator 


				i.  filtration,  capillary bed permeability 


		5. directly inhibit renin secretion at the juxtaglomerular apparatus 


			a. directly ¯ aldosterone by inhibiting adrenal zona glomerulosa


			b. also inhibit AVP

XIX. Reproductive Endocrinology - Gonadal Axis