Η νευροϋπόφυση: οι ορμόνες Βαζοπρεσσίνη και Οξυτοκίνη

Η νευροϋπόφυση: οι ορμόνες Βαζοπρεσσίνη και Οξυτοκίνη

ραστικότητα Lys-Βαζοπρεσσίνης : 65-70% της αντιδιουρητικής δράσης της Arg-Βαζοπρεσσσίνης

Figure 14-11. Structure of bovine prepropressophysin (left) and prepro-oxyphysin (right). Gly in the 10 position of both peptides is necessary for amidation of the Gly residue in position 9. aa, amino acid residues. (Reproduced, with permission, from Richter D: Molecular events in expression of vasopressin and oxytocin and their cognate receptors. Am J Physiol 1988;255:F207.)

Περιεκτικότητα πλάσματος σε ΑDH :1 pmol/l Χρόνος υποδιπλασιασμού ADH : 8-20min Χρόνος υποδιπλασιασμού OT: 5 min Mεταβολισμός ADH σε ήπαρ και νεφρούς ADH + ΟΤ ευρίσκεται επίσης σε υπερχιασματικό πυρήνα, γενννητικούς αδένες, φλοιό επινεφριδίων ΑDH V 1A (αγγειοσυσταλτική δράση), V 1B (δράση στα κορτικοτρόπα κύτταρα) PLC & Ca 2+ ΑDH V 2 (αντιδιουρητική δράση) αδενυλκυκλάση

Key Aspects of Posterior Pituitary Hormones Oxytocin Arginine vasopressin Receptor G q/11 protein-coupled G protein - coupled (V 1 R, G q/11, V 2 R, G s ) Second messenger Phospholipase (V 1 R) Phospholipase C [Ca 2+ ] i C [Ca 2+ ] i (V 2 R) Adenylate cyclase camp Target organ or cells Physiologic effects Uterus Mammary myoepithelial cells Uterine contraction Milk ejection V 2 R; kidney collecting ducts V 1 R; smooth muscle cells Increased H 2 O permeability Vasoconstriction

JOSE ANTUNES-RODRIGUES, MARGARET DE CASTRO, LUCILA L. K. ELIAS, MARCELO M. VALENC A, AND SAMUEL M. McCANN. Neuroendocrine Control of Body Fluid Metabolism. Physiol Rev 2004 84:169-208

Figure 14-7. Relation of plasma osmolality to thirst in healthy adult humans during infusion of hypertonic saline. The intensity of thirst is measured on a special analog scale. (Reproduced, with permission, from Thompson CJ et al: The osmotic thresholds for thirst and vasopressin release are similar in healthy humans. Clin Sci Lond 1986;71:651.)

Figure 14-12. Responses of magnocellular neurons to stimulation. The tracings show individual extracellularly recorded action potentials, discharge rates, and intramammary duct pressure. A: Response of an oxytocin-secreting neuron. HFD, high-frequency discharge; ME, milk ejection. Stimulation of nipples started before the onset of recording. B: Responses of a vasopressin-secreting neuron, showing no change in the slow firing rate in response to stimulation of nipples and a prompt increase in the firing rate when 5 ml of blood was drawn, followed by typical phasic discharge. (Tracings from Wakerly JB: Hypothalamic neurosecretory function: Insights from electrophysiological studies of the magnocellular nuclei. IBRO News 1985;4:15.)

Figure 14-13. Relation between plasma osmolality and plasma vasopressin in healthy adult humans during infusion of hypertonic saline. LD, limit of detection. (Reproduced, with permission, from Thompson CJ et al: The osmotic thresholds for thirst and vasopressin are similar in healthy humans. Clin Sci [Colch] 1986;71:651.)

Figure 14-14. Relation of mean arterial blood pressure to plasma vasopressin in healthy adult humans in whom a progressive decline in blood pressure was induced by infusion of graded doses of the ganglionic blocking drug trimethaphan. The relation is exponential rather than linear. (Drawn from data in Baylis PH: Osmoregulation and control of vasopressin secretion in healthy humans. Am J Physiol 1987;253:R671.)

Figure 14-15. Effect of hypovolemia and hyper-volemia on the relation between plasma vasopressin (pavp) and plasma osmolality (posm). Seven blood samples were drawn at various times from ten normal men when hypovolemia was induced by water deprivation (colored circles, dashed line) and again when hypervolemia was induced by infusion of hypertonic saline (black circles, solid line). Linear regression analysis defined the relationship pavp = 0.52 (posm - 283.5) for water deprivation and pavp = 0.38 (posm - 285.6) for hypertonic saline. LD, limit of detection. Note the steeper curve as well as the shift of the intercept to the left during hypovolemia. (Courtesy of CJ Thompson.)

Figure 32-7. Circumventricular organs. The neurohypophysis (NH), organum vasculosum of the lamina terminalis (OVLT, supraoptic crest), subfornical organ (SFO), and area postrema (AP) are shown projected on a sagittal section of the human brain. SCO, subcommissural organ; PI, pineal.