Aldosterone physiological effects

An account of the principles which help to understand how hormones achieve their roles in the body is given in Chapter 12. The understanding is based on separation of the effects of hormones into three components the action, the effects (biochemical and physiological) and the function. A steroid hormone binds to a cytosolic intracellular receptor, which then moves into the nucleus where it binds to DNA at a specific site (the steroid response element) and activates genes which result in the formation of proteins that elicit biochemical and physiological effects. This is discussed for cortisol in Chapter 12 and aldosterone in Chapter 22. Much of the interest in the reproductive steroid hormones is in the physiological effects and how these account for their functions. 

A. Angiotensin II has diverse physiological effects, including stimulating the synthesis and release of aldosterone from the adrenal cortex. This effect of angiotensin II results in fluid and water retention. The other answers are incorrect in that angiotensin II... 

Spironolactone competitively inhibits the physiologic effects of the adrenocortical hormone aldosterone on the distal tubules, thereby producing increased excretion of sodium chloride and water, and decreased excretion of potassium, ammonium, titratable acid, and phosphate. Spironolactone is a potassium-sparing diuretic that has diuretic activity only in the presence of aldosterone, and its effects are most pronounced in patients with aldosteronism. Spironolactone does not interfere with renal tubular transport mechanisms, and does not inhibit carbonic anhydrase. 

Licorice (Glycyrrhiza glabra) Licorice has physiological effects similar to aldosterone (antihypertensive) and corticosteroids (antiinflammatory). 

Cyclic GMP is made from GTP by the enzyme gua-nylyl cyclase, which exists in soluble and membrane-bound forms. Each of these isozymes has unique physiologic properties. The atriopeptins, a family of peptides produced in cardiac atrial tissues, cause natriuresis, diuresis, vasodilation, and inhibition of aldosterone secretion. These peptides (eg, atrial natriuretic factor) bind to and activate the membrane-bound form of guanylyl cyclase. This results in an increase of cGMP by as much as 50-fold in some cases, and this is thought to mediate the effects mentioned above. Other evidence links cGMP to vasodilation. A series of compounds, including nitroprusside, nitroglycerin, nitric oxide, sodium nitrite, and sodium azide, all cause smooth muscle re-... 

Assuming the capsular pressures opposing the movement of water out of the blood and into the top of the nephron are constant, the net filtration pressure is due largely to the blood pressure. Any fall in blood pressure can have a dramatic effect on the efficiency of filtration and therefore clearance of waste materials. So important is the pressure within the renal vasculature that the kidney is critical in regulating systemic blood pressure via the renin-angiotensin-aldosterone (RAA) axis, a physiological process which relies on transport mechanisms within the renal tubules. 

This chapter is divided into three sections. The first section covers renal tubule transport mechanisms. The nephron is divided structurally and functionally into several segments (Figure 15-1, Table 15-1). Many diuretics exert their effects on specific membrane transport proteins in renal tubular epithelial cells. Other diuretics exert osmotic effects that prevent water reabsorption (mannitol), inhibit enzymes (acetazolamide), or interfere with hormone receptors in renal epithelial cells (aldosterone receptor blockers). The physiology of each segment is closely linked to the basic pharmacology of the drugs acting there, which is discussed in the second section. Finally, the clinical applications of diuretics are discussed in the third section. 

Umminger, B.L. and Gist, D.H. (1973). Effects of thermal acclimation on physiological responses to handling stress, cortisol and aldosterone injections in the goldfish, Carassius auratus. Comparative Biochemistry and Physiology 44A, 967-977. 

Kotchen, T. A., G. P. Guthrie, J. H. Galla, R. Luke, and W. J. Welch. 1983. Effects of NaCl on renin and aldosterone responses to potassium depletion. American Journal of Physiology 244 E164-169. 

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