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This Article Full Text Full Text (PDF) All Versions of this Article: 295/2/E463    most recent 90385.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Google Scholar Articles by Jiang, Q. Articles by Wong, A. O. L. PubMed PubMed Citation Articles by Jiang, Q. Articles by Wong, A. O. L.

Grass carp somatolactin: I. Evidence for PACAP induction of somatolactin- and -β gene expression via activation of pituitary PAC-I receptors

¹School of Biological Sciences, University of Hong Kong, Hong Kong, China; ²Department of Dermatology, Massachusetts General Hospital, Charlestown, Massachusetts; and ³Department of Biochemistry, Chinese University of Hong Kong, Shatin, Hong Kong, China

Submitted 22 April 2008 ; accepted in final form 29 May 2008

Somatolactin (SL), the latest member of the growth hormone/prolactin family, is a novel pituitary hormone with diverse functions. At present, SL can be identified only in fish but not in tetrapods and its regulation at the pituitary level has not been fully characterized. Using grass carp as a model, we examined the direct effects of pituitary adenylate cyclase-activating polypeptide (PACAP) on SL secretion and synthesis at the pituitary cell level. As a first step, the structural identity of grass carp SL, SL and SLβ, was established by 5'/3'-rapid amplification of cDNA ends. These two SL isoforms are single-copy genes and are expressed in two separate populations of pituitary cells located in the pars intermedia. In the carp pituitary, PACAP nerve fibers were detected in the nerve tracts of the neurohypophysis and extended into the vicinity of pituitary cells forming the pars intermedia. In primary cultures of grass carp pituitary cells, PACAP was effective in stimulating SL release, cellular SL content, and total SL production. The increase in SL production also occurred with parallel rises in SL and SLβ mRNA levels. With the use of a combination of molecular and pharmacological approaches, PACAP-induced SL release and SL gene expression were shown to be mediated by pituitary PAC-I receptors. These findings, as a whole, suggest that PACAP may serve as a hypophysiotropic factor in fish stimulating SL secretion and synthesis at the pituitary level. Apparently, PACAP-induced SL production is mediated by upregulation of SL and SLβ gene expression through activation of PAC-I receptors.

pituitary adenylate cyclase-activating polypeptide; grass carp pituitary cells

This article has been cited by other articles:

				Q. Jiang, M. He, X. Wang, and A. O. L. Wong Grass carp somatolactin: II. Pharmacological study on postreceptor signaling mechanisms for PACAP-induced somatolactin-{alpha} and -{beta} gene expression Am J Physiol Endocrinol Metab, August 1, 2008; 295(2): E477 - E490. [Abstract] [Full Text] [PDF]