TRANSCRIPTIONAL ACTIVITIES IN THE PITUITARIES OF CHANNEL CATFISH BEFORE AND AFTER INDUCED OVULATION BY INJECTION OF CARP PITUITARY EXTRACT AS REVEALED BY EXPRESSED SEQUENCE TAG ANALYSIS

Expressed sequence tag (EST) analysis was adopted to address physiolog ical changes after injection of carp pituitary extract for induction o f ovulation. ESTs were analyzed from cDNA libraries constructed from m RNA isolated from channel catfish (Ictalurus punctatus) pituitaries be fore and after induction of ovulation by injection of carp pituitary e xtract. One hundred randomly picked clones were analyzed. Of the seque nces generated, a large percentage (59%) of ESTs were identified as kn own genes by identity comparisons. These 59 clones of known gene produ cts represent transcriptional products of 30 genes. The 41 clones of u nknown gene products represent 33 genes. Expression of gonadotropin (G tH) alpha-subunit (149%) and prolactin (176%) was slightly enhanced as a result of induced ovulation. Large increases in frequencies of seve ral peptide hormones were observed as a result of induced ovulation: G tH beta-I, 486%; GtH beta-II, 933%; growth hormone, 393%; pro-opiomela nocortin (POMC), 345%. POMC represented about 21% of all transcription al activity in the pituitaries after induced ovulation. This is the fi rst study addressing physiological changes after injection of carp pit uitary extract, a procedure widely used in catfish hatcheries.