Skip to main content
ARS Home » Plains Area » Houston, Texas » Children's Nutrition Research Center » Research » Publications at this Location » Publication #81186
Title: ADIPOSE TISSUE BETA-ADRENERGIC AND A1 ADENOSINE RECEPTORS IN SUCKLING PIGS

Author
item Mersmann, Harry
item CAREY, GALE - UNIV. OF NEW HAMPSHIRE
item SMITH, E. - BAYLOR COLL OF MEDICINE

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/27/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: During the first few weeks after pigs are born, there are major changes in the way that the fat in fat cells is metabolized in the body. Two of the major receptors in fat cells that control this type of metabolism are the beta-adrenergic receptors and the adenosine A1 receptors. The second type of receptor works in opposition to the first type. We wanted to obtain an understanding of the role and development of these receptors in piglets, the animal model for the human infant. We studied fat tissue in two groups of pigs: crossbred and genetically obese suckling pigs which were newborn, 3, 10 and 17 days of age. We found that the beta-adrenergic receptors changed with age in both types of pigs; there were fewer of these receptors at younger ages, which might contribute to the rapid growth of fat cells during this period. There were no measurable adenosine A1 receptors at any of the ages that we tested in this early period after birth, which means this type of receptor is not important in the rapid cell growth that occurs during the suckling period.

Technical Abstract: During the first few weeks after birth, major changes occur in porcine adipocyte lipid metabolism. Two of the important receptors controlling lipid metabolism in adipocytes are the B-adrenergic receptors (B-AR) and the A1 adenosine receptors (A1R). To gain insight into the role of these receptors in modulating neonatal adipocyte lipid metabolism, receptor affinity and number were measured in suckling pigs. Adipose tissue from crossbred (X-Bred) and genetically obese suckling pigs at 0,3,10, and 17 d of age was used to prepare crude membranes. The B-AR and A1R number and affinity were measured in membranes by equilibrium saturation binding with radioligands. Obese pigs were smaller than X-Bred pigs (average weight = 1.62 and 2.43 kg for obese and X-Bred, respectively; P<.01). Osmium-fixed adipocytes were larger in obese pigs than in X-Bred pigs (average cell diameter = 34.4 and 30.1 mum for obese and X-Bred, respectively; P<.01). In nboth obese and X-Bred pigs, the affinity of the B-AR for iodocyanopindolol was greater (lower Kd) at 17 d than at the younger ages (average Kd = 177 pM at 17 d compared to >330 pM at younger ages; age effect P<.01). In both obese and X-Bred pigs, the B-AR number was lowest at 10 d of age (average number + 41 at 10 d compared to >65 fmol/mg protein at older and younger ages; age effect P=.03). The higher B-AR and the lower number in younger animals suggest lesser adrenergic regulation, which would allow greater anabolic lipid metabolism to proceed during the neonatal period, when adipocytes increase four- to sixfold in volume. There were no measurable A1R at any of these early ages; thus, adenosine control mechanisms to counteract the B-AR and provide negative controls to lipid accretion are not operable in suckling pigs.