Neurohypophyseal hormones

Table 1. Structures of the Neurohypophyseal Hormone-Like Peptides, ...

Several human receptors for the neurohypophyseal hormones have been cloned and the sequences elucidated. The human V2 receptor for antidiuretic hormone presumably contains 371 amino acids and seven transmembrane segments and activates cycHc AMP (76). The oxytocin receptor is a classic G-protein-coupled type of receptor with a proposed membrane topography also involving seven transmembrane components (84). A schematic representation of the oxytocin receptor stmcture within the membrane is shown in Eigure 4 (85). 

M. Rholam and P. Nicolas, Conformational flexibility of neurophysin as investigated by local motions of fluorophores. Relationships with neurohypophyseal hormone binding,... 

Myometrial stimulants. The neurohypophyseal hormone oxytocin (p. 242) is given parenterally (or by the nasal or buccal route) before, during, or after labor in order to prompt uterine contractions or to enhance them. Certain prostaglandins or analogues of them (p. 

Bergman RN, Hechter O. Neurohypophyseal hormone-responsive renal adenylate cyclase. IV. A random-hit matrix model for coupline in a hormone-sensitive adenylate cyclase system. J Biol Chem 1978 253 3238-3250. 

Structure-Activity Relationships. Oxytocin and vasopressin are neurohypophyseal hormones synthesized in the hypothalamus and then transported along with their carrier proteins to the posterior lobe of the pituitary... 

C. W. Smith, Ed., The Peptides Analysis, Synthesis, and Biology. Chemistry, Biology and Medicine of Neurohypophyseal Hormones and Their Analogs, Vol. 8, Academic Press, New York, 19Sl,pp. 1-370. 

M. Lebl inK. dost, M. Lebl, and F. Brtnik, Eds., Handbook of Neurohypophyseal Hormone Analogs, Vol. 1, CRC Press, Boca Raton, FL, 1987. 

The anterior pituitary is not innervated by nerve fibers from the hypothalamus but is well vascularized by the portal blood that drains the median eminence. The portal blood flows primarily from the median eminence to the anterior pituitary however, some vessels may transport blood in the opposite direction (retrograde flow). The posterior pituitary consists mainly of nerve endings of hypothalamic magnocellular neurons and contains no portal connections with the hypothalamus its vascular connections are largely independent of those in the anterior pituitary. The hormones of the posterior pituitary (neurohypophyseal hormones) were discussed above. 

The neurohypophyseal hormones oxytocin and vasopressin are involved in autism. Elevated levels of blood serotonin occur in one third to two thirds of persons with autism. Parents of autistic children often have elevated blood serotonin levels, as well as an increased incidence of depression, obsessions, and compulsions. 

Neurohypophyseal hormones, peptide hormones secreted from the neurohypophysis, the posterior lobe of the pituitary, which is anatomically distinct from the adenohy-... 

Vasotocin (VT), H-Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Arg-Gly-NH2 (disulfide bond Cys -Cys ), the evolutionary precursor of the neurohypophyseal hormones. VT has been found in the pineal body of mammals and in the cerebrospinal fluid of humans. It is responsible for the regulation of water and mineral metabolism of lower vertebrates. During transition from the cyclostomata to fish, a gene duplication occurred which resulted in the formation of oxytocin and vasopressin. Only the replacement of Ile in VT by Phe led to vasopressin as the mammalian hormone. Precursors of VT (- hydrins) have been isolated from the pars intermedia of Rana esculenta [F. L. Moore, C. A. Lowry, Comp. Biochem. Physiol. C Pharmacol. Toxicol. Endocrinol. 1998, 119, 251]. 

The posterior lobe of the pituitary gland, the neurohypophysis, generally secretes two hormones of a family of nine found interspecifically. The same hormones are usually found in a zoological class, and the structure varies by only one or two residues among classes. These neurohypophyseal hormones are nonapeptides with a 1,6-disulfide bridge. In humans these hormones are oxytocin, which plays a role in lactation and parturition by causing smooth muscle contraction, and vasopressin, which has a homeostatic role in controlling water balance. 

Of the neurohypophyseal hormones, oxytocin was first crystallized in 1952 (Pierce et ai, 1952) as the flavionate, but the crystals were unsuitable for X-ray analysis. The first of many syntheses of the hormone was carried out by du Vigneaud et ai (1953), and a variety of crystalline salts of oxytocin (Rudko et ai, 1971) and deaminooxytocin analogs (Low and Chen, 1966 Chiu et ai, 1969) have been crystallized. Crystals of deaminooxytocin (and probably also deamino-6-selenooxytocin) crystallize in P2j (two molecules in the asymmetric unit) with pseudo-C2 symmetry. High-resolution X-ray data ( 1 A resolution) on both these forms have been collected, and the structure analysis is being pursued by a combination of isomorphous replacement and vector superposition techniques and direct methods (S.P. Wood, I. J. Tickle, Y. Mascarenhas, T. L. Blundell, and V. Hruby, unpublished results, 1980). 

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