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 Ý [K+]



		6. Feedback


			a. Ang2 & 3 suppress secretion of renin


			b. indirect negative feedback


				i. aldosterone ®+ Ý Na+ reabsorption


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


				iii. drinking, antidiuresis ® Ý BP


			c. Angiotensin I ®+ Ý Epi/NE (adrenal medulla) ® b2 ®+  Ý 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 Ý Cl-, PO4-, Ca++ excretion 


			b. stimulated directly by Ý plasma Na+


		4. relax smooth muscle


			a. vasodilator 


				i. Ý filtration, Ý capillary bed permeability 


		5. directly inhibit renin secretion at the juxtaglomerular apparatus 


			a. directly ¯ aldosterone by inhibiting adrenal zona glomerulosa


			b. also inhibit AVP