Synthesis, turnover, and release of peptides from the neurohypophysis of the Jerboa Jaculus orientalis.
Peptide contents of neural lobes from adult jerboas (Jaculus orientalis) under different states of hydration were determined by radioimmunoassay. The amounts of vasopressin, oxytocin, and their associated neurophysins in animals dehydrated for up to 4 weeks were not significantly different from those of controls. The different neurohypophyseal peptide were separated on two different types of gradient using reverse-phase high-performance liquid chromatography. The shape of the chromatograms suggests that, in contrast to the case of the rat, for which only three types of neurophysins have been shown, there are, in jerboa, many subspecies of neurophysins. This was also shown using two-dimensional electrophoresis. Injection of [35S]cysteine into the supraoptic nucleus followed by HPLC of extracts from the neural lobes from animals under different states of dehydration showed that the labeled material is not released any faster in dehydrated animals than in controls. Labeled vasopressin, oxytocin, and neurophysins could still be detected by HPLC 4 weeks after injection. Neural lobes from animals injected with [35S]cysteine were perfused in vitro and the release of neuropeptides was triggered by bursts of electrical pulses and also by K(+)-induced depolarization. The amplitude of the rate constant for release and the amounts of vasopressin and of radiolabeled material released were similar in animals dehydrated for up to 3 weeks and in controls. Under physiological conditions similar to those that would be expected to occur in their natural habitat, the jerboas appear to have a hypothalamoneurohypophyseal system which is down-regulated.
Raji
A
A
Centre de Neurochimie, Strasbourg, France.
Nordmann
J J
JJ
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003545:Cysteine / Q000378:metabolism; D004558:Electric Stimulation; D066298:In Vitro Techniques; D009479:Neuropeptides / Q000096:biosynthesis* / Q000302:isolation & purification / Q000378:metabolism; D009481:Neurophysins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D010121:Oxytocin / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D010904:Pituitary Gland, Posterior / Q000187:drug effects / Q000502:physiology*; D011188:Potassium / Q000494:pharmacology; D012377:Rodentia / Q000378:metabolism*; D014667:Vasopressins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism
D009479:Neuropeptides; D009481:Neurophysins; D014667:Vasopressins; D010121:Oxytocin; D003545:Cysteine; D011188:Potassium