Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 3/15/2000
Publication Date: N/A
Technical Abstract: Agouti-related peptide (AGRP) is a 131 amino acid peptide produced in the hypothalamus and other tissues. AGRP stimulates appetite in rodents when administered centrally, and acts as a melanocortin receptor antagonist, blocking the appetite-suppressing activity of alpha-MSH. A 226 bp cDNA was generated from porcine hypothalamic RNA by use of a reverse transcription-polymerase chain reaction (RT-PCR) and primers designed from the published human AGRP cDNA sequence. This PCR fragment was then cloned into a vector and sequenced. The confirmed porcine AGRP cDNA sequence was found to be 84% homologous to the corresponding human sequence. An AGRP cRNA probe was transcribed from this clone and used to examine AGRP expression in several porcine tissues via RT-PCR followed by Southern hybridization. Although the hypothalamus was found to be the major site of AGRP gene expression, several other tissues expressed AGRP mRNA as well, including anterior pituitary, thymus, testis, adrenal and liver. A larger (650 bp) PCR fragment was found to hybridize to the porcine AGRP cRNA in spleen, adrenal, and liver tissues; this fragment was cloned and sequenced and found to be an AGRP cDNA which contains intron III, indicating the possibility of splice variants existing in these tissues. Next, hybridization assays were performed to quantitate differences in hypothalamic AGRP gene expression in large (5.098+/.093 kg, n = 11) and small (3.966+/.073 kg, n = 12) 14-d-old weanling piglets. Large piglets expressed greater amounts of AGRP mRNA than did small piglets as measured in relative densitometric units after normalization to 18S ribosomal RNA (1.382+/.059 vs. 0.912+/.084, P = 0.002). These data represent the first characterizations of AGRP gene expression in a livestock species.