Effects of hypothalamic factors on somatolactin secretion from the organ-cultured pituitary of rainbow trout.
The profile of daily release of somatolactin (SL) and effects of hypothalamic factors on SL secretion from the organ-cultured pituitary of rainbow trout were examined. The daily release of SL was relatively high (340-380 ng/pituitary/day) for the first 2 days and then decreased. After Day 5, the SL release was maintained at a low level (30-50 ng/pituitary/day) until the end of the experiment at Day 7. The secretory patterns of SL differed from those of growth hormone (GH) and prolactin (PRL); GH secretion was consistently high (15-20 microg/pituitary/day), whereas PRL secretion was low (10 ng/pituitary/day) during the experiment. SL release was not stimulated by calcium ionophore on Days 2 and 6, suggesting that SL release was maximal. Dopamine and epinephrine, added separately to the medium, inhibited SL release. In contrast, serotonin, corticotropin-releasing factor, and gonadotropin-releasing hormone stimulated the dopamine-inhibited SL release. Thus, SL secretion is concluded to be under hypothalamic control and regulated by mechanisms different from those affecting PRL and GH secretion.
Kakizawa
S
S
Ocean Research Institute, University of Tokyo, Nakano, Tokyo, Japan.
Kaneko
T
T
Hirano
T
T
D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D003346:Corticotropin-Releasing Hormone / Q000494:pharmacology; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D004298:Dopamine / Q000494:pharmacology; D004837:Epinephrine / Q000494:pharmacology; D029941:Fish Proteins; D006023:Glycoproteins / Q000378:metabolism*; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D013006:Growth Hormone / Q000187:drug effects / Q000378:metabolism; D007476:Ionophores / Q000494:pharmacology; D017686:Oncorhynchus mykiss; D009924:Organ Culture Techniques; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism*; D010907:Pituitary Hormones / Q000378:metabolism*; D011388:Prolactin / Q000187:drug effects / Q000378:metabolism; D012701:Serotonin / Q000494:pharmacology; D013997:Time Factors
D029941:Fish Proteins; D006023:Glycoproteins; D007476:Ionophores; D010907:Pituitary Hormones; C064448:somatolactin protein, fish; D012701:Serotonin; D007987:Gonadotropin-Releasing Hormone; D000001:Calcimycin; D011388:Prolactin; D013006:Growth Hormone; D003346:Corticotropin-Releasing Hormone; D004298:Dopamine; D004837:Epinephrine; D004121:Dimethyl Sulfoxide