PARENT SESSION
Pregnancy and Parturition

TEMPORAL AND SPATIAL PROFILES OF LEPTIN AND ITS RECEPTOR EXPRESSION IN BOVINE PLACENTA.

Takahashi, Toru¹, kizaki, Keiichiro¹, Yamada, Osamu¹, Imai, Kei¹, Takezawa, Toshiaki¹, Hashizume, Kazuyoshi¹, ¹

ABSTRACT- Leptin, a 16 kDa protein encoded by the ob gene, is postulated to play a role on the regulation of satiety. However, recent studies indicate that leptin is expressed in the placenta suggesting a plausible role during pregnancy. At present, there is no report on leptin expression in bovine placenta. Therefore, the objective of this study was to determine the temporal and spatial expression profiles of leptin and its receptor in bovine placenta. The expression of bovine leptin and its receptor transcripts were determined by PCR-based semi-quantitative assay with total RNA isolated from the caruncle and the cotyledon on days 30, 60, 120 and 260 of gestation. Concurrently, a recombinant leptin was expressed in 293 cells following transfection of pRcRSV expression vector construct, purified and utilized for antibody generation. Anti-peptide antisera for leptin were also generated. The expression of leptin transcript was detected in both the caruncle and the cotyledon. There was a parallel increase in the expression of leptin transcript in the caruncle with advancement of gestation, whereas, it remained constant in the cotyledon. On the other hand, the expression of leptin receptor transcript increased with gestation in the cotyledon while remaining constant in the caruncle. Recombinant leptin expressed itself as a 16 kDa protein in 293 cells alike in native leptin produced by adipocytes. Antisera were raised for recombinant leptin and synthetic oligopeptides corresponding to amino acid sequence 21-40 and 91-110 of bovine leptin. Western blot analysis showed that all antisera reacted to bovine leptin and simultaneously the antigenic specificity was also confirmed. Antiserum for whole recombinant leptin was not neutralized by the peptides 21-40 and 91-110 suggesting some difference in antigen recognition when compared to those of anti-peptide antisera. Immunohistochemistry revealed that leptin protein was expressed in caruncle especially in the perivascular area. The latter is in agreement with our finding on mRNA expression. Results in the present study revealed a temporal and spatial specific expression of leptin and its receptor transcripts suggesting a function for leptin in the placentome. This study was supported in part by a Grants-in-aid from the ORCS, BRAIN and MAFF.

KEY WORDS: leptin, bovine, placenta