Polymorphism of somatolactin-producing cells in the goldfish pituitary: immunohistochemical investigation for somatolactin-α and -β

Abstract

Somatolactin (SL) is a pituitary hormone belonging to the growth hormone/prolactin family of adenohypophyseal hormones. In teleost fish, SL is encoded by one or two paralogous genes, namely SL-α and -β. Our previous studies have revealed that pituitary adenylate-cyclase-activating polypeptide stimulates SL release from cultured goldfish pituitary cells, whereas melanin-concentrating hormone suppresses this release. As in other fish, the goldfish possesses SL-α and -β. So far, however, no useful means of detecting the respective SLs immunologically in this species has been possible. In order to achieve this aim, we raised rabbit antisera against synthetic peptide fragments deduced from the goldfish SL-α and -β cDNA sequences. Using these antisera, we observed adenohypophyseal cells showing SL-α- and -β-like immunoreactivities in the goldfish pituitary, especially the pars intermedia (PI). Several cells in the PI showed the colocalization of SL-α- and -β-like immunoreactivities. Then, using single-cell polymerase chain reaction with laser microdissection, we examined SL-α and -β gene expression in adenohypophyseal cells showing SL-α- or -β-like immunoreactivity. Among cultured pituitary cells, we observed three types of cell: those that possess transcripts of SL-α, -β, or both. These results suggest a polymorphism of SL-producing cells in the goldfish pituitary.

The Octadecaneuropeptide Stimulates Somatolactin Release from Cultured Goldfish Pituitary Cells

“…Using these antibodies, we found that the two SL isoforms are co‐localised in several cells of the PI. Single‐cell PCR with laser microdissection confirmed that some cells co‐express SL‐α and SL‐β, whereas others only express SL‐α or SL‐β mRNAs, suggesting polymorphism of SL‐producing cells in the goldfish PI . We also examined the effect of ODN on SL‐α and SL‐β release from cultured goldfish pituitary cells.…”

“…We have recently raised two specific antisera against goldfish SL‐α and SL‐β . Using these antibodies, we found that the two SL isoforms are co‐localised in several cells of the PI.…”

“…Semiquantitative measurement of SL release was determined as total area of SL‐like immunoreactivity in six immunoblot membranes containing approximately 100–300 immunoblots, and was expressed as percentage to area of SL‐like immunoreactivity in the control group. We have recently raised specific rabbit antisera against synthetic peptide fragments deduced from goldfish SL‐α and SL‐β cDNA sequences . These antisera (anti‐SL‐α; dilution 1 : 4000; anti‐SL‐β, dilution 1 : 4000) have been used to study the effect of ODN on SL‐α and SL‐β release from cultured goldfish pituitary cells by immunoblotting as described above.…”

“…By contrast, ODN (at concentrations that were sufficient to stimulate SL release) did not affect SL-a and SLb mRNA levels in goldfish, suggesting that ODN does not activate the ERK cascade in SL cells. We have recently raised two specific antisera against goldfish SL-a and SL-b (57). Using these antibodies, we found that the two SL isoforms are co-localised in several cells of the PI.…”

Expression pattern of somatolactin in the Chinese sturgeon,Acipenser sinensisGray, 1835

“…() reported the distribution of SL cells in the pars intermedia (PI) in white sturgeon and common carp ( Cyprinus carpio ). Immunohistochemistry observation has shown that both forms of SL expressed in differing cell populations located in the PI of goldfish, but not in the RPD (rostral pars distalis), PPD, or caudal pars distalis (Azuma et al., ). Recently, some studies also reported the PI‐specific expression of SL such as in thin‐lipped gray mullet ( Liza ramada ) (Khalil et al., ), tabarana ( Salminus hilarii ) (Honji et al., ) and grass carp ( Ctenopharyngodon idella ) (Grandi et al., ).…”