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Cloning of a buffalo (Bubalus bubalis) prostaglandin F₂ receptor: changes in its expression and concentration in the buffalo cow corpus luteum

Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore 560 012, India and ¹ Department of Pharmacology and Toxicology, Veterinary College, University of Agricultural Sciences, Bangalore 560 024, India

Correspondence should be addressed to R Medhamurthy; Email: rmm{at}mrdg.iisc.ernet.in

Acting primarily through its specific G protein-coupled receptor termed FPr, prostaglandin (PG) F₂ induces regression of the corpus luteum (CL) at the end of a non-fertile oestrous cycle. This study was aimed at cloning a full-length cDNA for FPr and determining its expression and protein concentrations during different stages of CL development in the water buffalo. Serum progesterone and StAR expression were determined to establish temporal relationships between indices of steroidogenesis and changes in FPr expression at different stages of CL development. In contrast to the dairy cow, the stage IV CL (day 20 of the oestrous cycle) did not appear to be functionally regressed in the buffalo. Molecular cloning of a cDNA encoding the buffalo FPr yielded a full length 2193 bp FPr cDNA containing a single open reading frame encoding a 362 amino acid protein with seven putative membrane-spanning domains. The deduced buffalo FPr amino acid sequence possesses a high degree of identity with the other mammalian homologues. Steady state concentration of buffalo FPr transcript increased (P > 0.05) from stage I to stage II/III, and declined at 18 h post PGF₂ injection. The FPr concentration expressed as fmol/µg of plasma membrane protein showed an increase (P > 0.05) from stage I (1.98 ± 0.10), through stage II/III (2.42 ± 0.48) to stage IV (2.77 ± 0.18). High affinity FPr was observed in stage I (K_d 4.86 nmol) and stage II/III (K_d 6.28 nmol) while low affinity FPr (K_d 19.44 nmol) was observed in stage IV. In conclusion, we have cloned a full length FPr cDNA from buffalo cow CL and observed that FPr mRNA expression, receptor number and affinity did not vary significantly (P > 0.05) within the luteal phase of the oestrous cycle.