Vasopressin regulation

FIGURE 29—4 Mechanisms by which vasopressin increases the renal conservation of water. IMCD, inner medullary collecting duct TAL, thick ascending limb VRUT, vasopressin-regulated urea transporter. Thick and thin arrows denote major and minor pathways, respectively. 

Vasopressin regulates the excretion of water by the kidneys, as noted in the A Word about Some Naturally Occurring Peptides (on page 503). 

Vasopressin (antidiuretic hormone [ADH]) secretion increases in response to decreased blood volume and/or reductions in effective blood volume via a decrease in inhibitory tone from both low-pressure and high-pressure baroreceptors to the hypothalamus. The neuronal pathways that mediate hemodynamic regulation of... 

Vasopressin (Rtressin Synthetic) and its derivatives, namely lypressin (Diapid) and desmopressin (DDAVP), regulate the reabsorption of water by the kidneys. Vasopressin is secreted by the pituitary when body fluids must be conserved. An example of this mechanism may be seen when an individual has severe vomiting and diarrhea with little or no fluid intake. When this and similar conditions are present, die posterior pituitary releases the hormone vasopressin, water in die kidneys is reabsorbed into die blood (ie, conserved), and die urine becomes concentrated. Vasopressin exhibits its greatest activity on die renal tubular epithelium, where it promotes water resoqition and smooth muscle contraction throughout die vascular bed. Vasopressin has some vasopressor activity. 

Indicate the source, factors regulating the release, and physiological significance of the following vasoconstrictors catecholamines, angiotensin II, vasopressin, endothelin, and thromboxane A2... 

Vasopressin (antidiuretic hormone) is a peptide synthesized in the hypothalamus and secreted from the neurohypophysis of the pituitary gland. This substance plays an important role in the long-term regulation of blood pressure through its action on the kidney to increase reabsorption of water. The major stimulus for release of vasopressin is an increase in plasma osmolarity. The resulting reabsorption of water dilutes the plasma toward its normal value of 290 mOsM. This activity is discussed in more detail in Chapter 10 (the endocrine system) and Chapter 19 (the renal system). 

Vasopressin also plays an important role in short-term regulation of blood pressure through its action on vascular smooth muscle. This hormone is the most potent known endogenous vasoconstrictor. Two types of vasopressin receptors have been identified V, receptors mediate vasoconstriction... 

Diabetes insipidus occurs with a loss of vasopressin production in the Brattleboro rat model 330 Mutations and knockouts of peptide-processing enzyme genes cause a myriad of physiological problems 330 Neuropeptides play key roles in appetite regulation and obesity 330 Enkephalin knockout mice reach adulthood and are healthy 331 Neuropeptides are crucial to pain perception 331... 

The hypothalamic releasing factors regulate release of the anterior pituitary trophic hormones. As summarized in Figure 52-1, the releasing factors are produced in various neuronal groups within the hypothalamus and are transported to the median eminence for release into the portal circulation to the anterior pituitary. Neurons in the hypothalamus also produce the hormones oxytocin and vasopressin, which are released by the posterior pituitary into the blood. Therefore, it is not surprising that behavior and experience, which influence the hypothalamus, sometimes alter the secretion of these hypothalamic releasing factors and hormones. 

FIG. 5. Only non-capacitative Ca2+ entry occurs during receptor activation. Cells were stimulated with vasopressin (30 nM for 300 s) under conditions where both, neither or only one of the Ca2+ entry pathways were blocked. The same scale applies to all four traces, with the origin shown on each by a thick line. (Results taken from Moneer Taylor [2002].) The cartoon indicates that reciprocal regulation of the two pathways may allow rapid switching between stimulation (contraction evoked by Ca2+ entering via NCCE) and recovery (relaxation evoked by Ca2+ entering via CCE)... 

Zhu, X. and Wess, J. (1998) Truncated V2 vasopressin receptors as negative regulators of wild-type V2 receptor function. Biochemistry 37, 15773-15784. 

Altemus, et al Pigott, T., Kalogeras, K.., 1992. Abnormalities in the regulation of vasopressin and corticotropin releasing factor secretion in obsessive-compulsive disorder. Archive of General Psychiatry 49 9-20. 

Androgen AR Human cell line Cancer, andropause, menopause, Sjogren s syndrome, idiopathic hirsutism, infertility, hypertension, mood disorders, diabetes, cystic fibrosis Immune modulation, vascular hemodynamics, neuroprotection, skeletal development, reproduction, maintenance of neuronal morphology, regulation of vasopressin Vla expression, prostatic blood flow and LH production... 

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