Feed restriction and insulin treatment affect subsequent luteal function in the immediate postovulatory period in pigs: Progesterone production in vitro and messenger ribonucleic acid expression for key steroidogenic enzymes

Progesterone production and release in vitro, and mRNA expression for key s teroidogenic enzymes, were studied in luteal tissue recovered in the immedi ate postovulatory period from cyclic gilts allocated to one of three treatm ents: moderate feed restriction during the first (RH) or second week of the estrous cycle, with (HR+I) or without (HR) concomitant injections of long- acting insulin. Time of feed restriction affected neither progesterone prod uction or release, nor mRNA expression for several key steroidogenic enzyme s. However, luteal tissue from RH but not from HR gilts responded to LH sti mulation by increasing progesterone production and release (P < 0.05), Insu lin treatment increased progesterone production and release, restored lutea l tissue responsiveness to LH, up-regulated steroidogenic enzyme mRNA expre ssion, and down-regulated the tissue inhibitor of metalloproteinase-1 mRNA expression in HR+I compared with HR gifts (P < 0.05). In vitro progesterone production and gene expression were affected by time of tissue collection after ovulation in RH and HR gilts but not in HR+I gilts, and were correlat ed with temporal changes in oviductal and peripheral plasma progesterone co ncentrations, Inherent differences in luteal function therefore appear to m ediate latent effects of nutrition and insulin treatment on circulating pro gesterone concentrations in the critical postovulatory period in gilts.