Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 7/28/2000
Publication Date: N/A
Technical Abstract: The melanocortin type 4 receptor (MCR4) is a hypothalamic receptor signalling for appetite suppression when bound by its ligand, alpha-melanocyte stimulating hormone (alpha-MSH), a product of the pro-opiomelanocortin (POMC) transcript. The agouti-related protein (AGRP) is another hypothalamic hormone which acts as an antagonist, binding to MCR4 and thus blocking the appetite-suppressive effects of alpha-MSH. We have recently presented preliminary data on the regulation of AGRP expression in newly weaned pigs; however, concurrent data on the expressions of POMC and MCR4 are required to interpret the physiological significance of altered AGRP expression. A 245 bp cDNA was generated from porcine hypothalamic RNA by reverse-transcription-polymerase chain reaction (RT-PCR). The porcine MCR4 sequence was found to be 93% homologous to the corresponding human sequence, and was used to generate a cRNA probe for the efollowing experiment. Fourteen-day-old nursing pigs were either crossfostered to another sow or weaned onto starter diets containing 0 or 7% spray-dried plasma (n = 8/group). Piglets were further allocated by size into small (3.5-4.3 kg) and large (4.6-5.7 kg) groups. Piglets were sacrificed 4 d later for tissue collection. Hypothalamic MCR4 and POMC mRNA levels (relative to 28S rRNA) were evaluated by slot-blot hybridization. Hypothalamic POMC mRNA levels did not differ between weaning strategies or size (P>.1). MCR4 gene expression was higher in large pigs compared to small pigs (.482+/.036 vs .331+/.023, P=.0025), but expression did not differ among weaning groups (P>.3). These data represent the first characterizations of MCR4 gene expression in a livestock species.