DIFFERENTIAL EXPRESSION OF 2 PROOPIOMELANOCORTIN MESSENGER-RNAS DURING TEMPERATURE STRESS IN COMMON CARP (CYPRINUS-CARPIO L)

Pro-opiomelanocortin (POMC) is the precursor oi a number of biological ly active peptides, including adrenocorticotropic hormone, alpha-melan ocyte-stimulating hormone and beta-endorphin, which are released by th e pituitary glands of fish as well as mammals. To quantify the levels of expression of the two POMC mRNAs relative to one another during the response oi the common carp to temperature-induced stress, we used re verse transcriptase PCR combined with capillary electrophoresis and la ser-induced fluorescence detection. The ratio oi POMC-I mRNA to POMC-I I mRNA determined in wild-type and four isogenic carp strains was foun d to be strain-dependent and influenced by temperature. In strain E20 x R8, the ratio had altered in favour of POMC-I from 1:3.2 (POMC-I:POM C-II) in fish adapted to 24 degrees C to 1:1.2 in fish adapted to a de crease of 9 degrees C in ambient temperature. A rapid drop in temperat ure from 24 to 15 degrees C decreased the POMC mRNA ratio at the expen se of POMC-I from 1:1.9 in the control fish (strain E4 x R3R8) to 1:4. 2 3 h alter the temperature drop oi 9 degrees C. We conclude that both POMC genes are expressed in the common carp and that their expression ratio is strain-dependent and changes in response to ambient temperat ure.